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ANAPHY MIDTERM
Chapter 6 Skeletal System: Bones and
Joints
6.1 FUNCTIONS OF THE SKELETAL SYSTEM
- Support.
- Protection.
- Movement
- Storage.
- Blood cell production
Figure 6.1 Major Bones of the Skeletal System
- Skull
- Clavicle
- Sternum
- Ribs
- Vertebral column
- Humerus
- Radius
- Ulna
- Pelvis
- Femur
- Tibia
- Fibula
6.2 EXTRACELLULAR MATRIX
Connective tissues
Bone Cartilage Tendons Ligaments
The matrix
Collagen - tough, ropelike protein Ground substance Organic molecules As well as water and minerals Proteoglycans – consists of polysaccharides attaching to and encircling core proteins.
6.3 GENERAL FEATURES OF BONE
Four categories of bone:
Long bones are longer than they are wide. Short bones are approximately as wide as they are long Flat bones have a relatively thin, flattened shape Irregular bones include the vertebrae and facial bones
Structure of a Long Bone
A long bone serves as a useful model for illustrating the parts of a typical bone
Diaphysis – central shaft; yellow marrow (Adult) Epiphysis – Two ends; contain red marrow Articular cartilage – A thin layer that covers the ends of the epiphyses where the bone articulates (joins) with other bones. Epiphyseal plate – A long bone that is still growing has this. Growth plate. If stop growing, it becomes an epiphyseal line. Medullary cavity – These spaces are filled with soft tissue called marrow Yellow marrow consists mostly of adipose tissue. Red marrow consists of blood-forming cells Periosteum – consists of two layers and contains blood vessels and nerves. Endosteum – lined the surface of medullary cavity.
Histology of Bone
Periosteum and endosteum contain osteoblasts ( bone-forming cells ). Osteocytes – osteoblasts that become surrounded by matrix. Osteoclasts - bone-destroying cells; repair and remodeling by removing existing bone. Lamellae – thin sheets of extracellular matrix. Lacunae – spaces between lamellae where osteocytes are located. Canaliculi - tiny canals Compact bone – mostly solid matrix and cells
Also called cortical bone has more matrix and is denser fewer pores Osteons - predictable pattern of repeating units; consists of concentric rings of lamellae surrounding a central canal ( Haversian canal ); Spongy bone – consist of a lacy network of bone with many small, marrow-filled spaces. Very porous and is located in the epiphyses of long bones and lines the medullary cavity of long bones. less bone matrix Trabeculae - consists of delicate interconnecting rods or plates of bone No blood vessels penetrate the trabeculae and it has no central canals Nutrients exit vessels in the marrow
Bone Ossification
Ossification – is the formation of bone by osteoblasts. Intramembranous ossification – Bone formation that occurs within connective tissue membranes. Occurs when osteoblasts begin to produce bone within connective tissue membranes. Occurs primarily in the bones of the skull. Endochondral ossification – bone formation that occurs inside hyaline cartilage. base of the skull and most of the remaining skeletal system Cartilage cells, called chondrocytes , increase in number, causing the cartilage model to increase in size. Primary ossification center – The center part of the diaphysis, where bone first begins to appear Secondary ossification centers – form in the epiphyses
Bone Growth
Occurs by the deposition of new bone lamellae onto existing bone or other connective tissue.
Bone Remodeling
removal of existing bone by osteoclasts and the deposition of new bone by osteoblasts and occurs in all bone Bones are dynamic structures. The shape and composition of bones are constantly changing through bone remodeling.
6.4 BONE AND CALCIUM HOMEOSTASIS
Calcium homeostasis is maintained by three hormones:
Parathyroid hormone (PTH) from the parathyroid glands, vitamin D from the skin or diet, and calcitonin from the thyroid gland. PTH and vitamin D are secreted when blood calcium levels are too low Calcitonin is secreted when blood calcium levels are too high. Inhibits osteoclast activity. Maintains homeostatic blood calcium levels by decreasing calcium levels that are too high. PTH works through three simultaneous mechanisms to increase blood calcium levels.
- PTH indirectly stimulates osteoclasts to break down bone, which releases stored calcium into the blood.
- PTH stimulates the kidney to take up calcium from the urine and return it to the blood.
- PTH stimulates the formation of active vitamin D, which, in turn, promotes increased calcium absorption from the small intestine.
6.5 GENERAL CONSIDERATIONS OF BONE ANATOMY
Foramen – hole in a bone Canal or meatus – If the hole is elongated into a tunnel-like passage through the bone Fossa – A depression in a bone Tubercle or tuberosity – A rounded projection on a bone Process – sharp projection Condyle – smooth, rounded end of a bone, where it forms a joint with another bone
have extra articular facets on their lateral surfaces that articulate with the ribs Lumbar vertebrae Have large, thick bodies and heavy, rectangular transverse and spinous processes. Have massive body ( Serves its purpose ) Sacrum five sacral vertebrae are fused into a single bone Median sacral crest first four sacral vertebrae Sacral hiatus spinous process of the fifth vertebra that does not form site of “caudal” anesthetic injections Sacral promontory Used as a reference point to determine if the pelvic openings are large enough to allow for normal vaginal delivery of a baby. Coccyx, or tailbone four more-or-less fused vertebrae Easily fractured when a person falls by sitting down hard on a solid surface or in women during childbirth.
Rib Cage
Protects the vital organs within the thorax Prevents the collapse of the thorax during respiration. Consists of the thoracic vertebrae , the ribs with their associated cartilag es, and the sternum. Ribs and Costal Cartilages 12 pairs of ribs True ribs , ribs 1 – 7 , attach directly to the sternum by means of costal cartilages. False ribs , ribs 8 – 12 , do not attach directly to the sternum.
Ribs 8– 10 attach to the sternum by 1 cartilage Floating ribs – ribs 11 and 12 Sternum or breastbone Divided into three parts: Manubrium (handle), the body , Xiphoid (sword) process Jugular notch – locate between the ends of the clavicles Sternal angle – identifies the location of the second rib Xiphoid process – another important landmark of the sternum during cardiopulmonary resuscitation (CPR)
6.7 APPENDICULAR SKELETON
Consists of the bones of the upper and lower limbs , as well as the girdles , which attach the limbs to the axial skeleton
Pectoral Girdle or shoulder girdle
Consists of four bones Two scapulae – shoulder blade , is a flat, triangular bone. Two clavicles – collarbone , articulates with the scapula at the acromion process. first bone to begin ossification in the fetus may be fractured in the newborn during delivery it is the last to complete ossification Glenoid cavity where the head of the humerus connects to the scapula Spine A ridge that runs across the posterior surface of the scapula. Acromion process
A projection, extends from the scapular spine to form the point of the shoulder Coracoid process – provides for the attachment of arm and chest muscles.
Upper Limb
Consists of the bones of the arm, forearm, wrist, and hand
Arm Humerus o Head o Greater tubercle o Lesser tubercle o Deltoid tuberosity o Epicondyles Forearm Radius on the lateral (thumb) o radial tuberosity Ulna on the medial (little finger) o trochlear notch o olecranon process o coronoid process o styloid process Wrist Five metacarpal bones Five digits Phalanges (all have 3, but thumb have only 2)
Pelvic Girdle
Place where the lower limbs attach to the body
hip bones sacrum pelvis ilium ischium iliac crest anterior superior iliac spine pubic symphysis sacroiliac joints acetabulum obturator foramen pelvic inlet pelvic outlet
Lower Limb
The lower limb consists of the bones of the thigh, leg, ankle, and foot
Thigh – between the hip and the knee Femur o Head o Condyles o Epicondyles o Trochanters o Patella Leg – region between the knee and the ankle Tibia o Tibial tuberosity Fibula Ankle Prominence o medial malleolus o lateral malleolus Foot seven tarsal talus metatarsal phalanges distal row is MILC o M edial, I ntermediate, and L ateral cuneiforms and the C uboid. proximal three bones is N o T hanks C ow o N avicular, T alus, and C alcaneus.
6.8 JOINTS
Joints or articulations Commonly named according to the bones or portions of bones that join together structurally as fibrous, cartilaginous, or synovial functional categories according to their degree of motion synarthroses (nonmovable joints), amphiarthroses (slightly movable joints), or diarthroses (freely movable joints)
6.9 EFFECTS OF AGING ON THE SKELETAL SYSTEM AND
JOINTS
Quality and quantity of bone matrix. Formation by osteoblasts becomes slower than the rate of matrix breakdown by osteoclasts. age 40 , loss of bone of 0.3–0.5% a year increase 10-fold in women after menopause 3 – 5% a year for approximately 5–7 years Increasing physical activity and taking dietary calcium and vitamin D supplements. Intensive exercise can even reverse loss of bone matrix. Osteoporosis or porous bone , is a loss of bone matrix. 2.5 times more common in women Women lose approximately one-half , and men one-quarter , of their spongy bone
Chapter 7 Muscular System
7.1 FUNCTIONS OF THE MUSCULAR SYSTEM
- Movement of the body.
- Maintenance of posture.
- Respiration
- Production of body heat.
- Communication
- Constriction of organs and vessels.
- Contraction of the heart
7.2 GENERAL PROPERTIES OF MUSCLE TISSUE
Muscle tissue has four major functional characteristics :
Contractility – ability of muscle to shorten forcefully, or contract. Excitability – capacity of muscle to respond to a stimulus. Extensibility – means that a muscle can be stretched beyond its normal resting length and still be able to contract Elasticity – ability of muscle to recoil to its original resting length
7.3 CHARACTERISTICS OF SKELETAL MUSCLE
Skeletal Muscle Structure
Or striated muscle , with its associated connective tissue, constitutes approximately 40% of body weight. Skeletal muscle is so named because many of the muscles are attached to the skeletal system. Connective Tissue Coverings of Muscle Epimysium / muscular fascia – connective tissue sheath Fascicles – visible bundles Perimysium – loose connective tissue that separates muscle fascicles from each other Muscle fibers – fascicles is subdivided into separate muscle cells Endomysium – loose connective tissue that surrounds each muscle fiber. Muscle Fiber Structure Single cylindrical cell , with several nuclei located at its periphery. Sarcolemma – cell membrane of the muscle fiber. Transverse tubules , or T tubules – tubelike inward folds in Sarcolemma. Sarcoplasmic reticulum – smooth endoplasmic reticulum. Have high concentration of Ca2+ which plays a major role in muscle contraction. Sarcoplasm – cytoplasm of a muscle fiber Myofibrils – bundles of protein filaments. Myofibrils consist of two major kinds of protein fibers : o Actin myofilaments o Myosin myofilaments - gives skeletal muscle its striated appearance Terminal cisternae – enlarged portions Sarcomeres Basic structural and functional unit of a skeletal muscle smallest portion of a skeletal muscle capable of contracting
1 sarcomere extends from one Z disk to the next Z disk Z disks - separate one sarcomere from the next. Network of protein fibers that forms a stationary anchor for actin myofilaments to attach. Myosin myofilaments - gives skeletal muscle its striated appearance I bands o light-staining bands o extends toward the center of the sarcomere o includes a Z disk o Consist of only actin myofilaments. A band o dark-staining band o extends the length of the myosin myofilaments o H zone - lighter-staining region at the center of A band; contains only myosin myofilaments o M line - consists of fine protein filaments Actin and Myosin Myofilaments Actin myofilaments , or thin filaments , are made up of three components: o Actin strands - have attachment sites for the myosin. o Troponin - have binding sites for Ca2+ o Tropomyosin - block the myosin myofilament binding sites on the actin myofilaments Myosin myofilaments , or thick myofilaments o Myosin heads three important properties: (1) The heads bind to attachment sites on the actin myofilaments; (2) They bend and straighten during contraction; and (3) They break down ATP, releasing energy.
SMOOTH MUSCLE
Excitability of Muscle Fibers
Muscle fibers are highly specialized, electrically excitable cells. Electrically excitable cells are polarized.
Energy Requirements for Muscle Contraction
Muscle fibers are very energy-demanding cells whether at rest or during any form of exercise. This energy comes from either ATP production:
Aerobic (with O2)
- occurs mostly in mitochondria
- requires O2 and breaks down glucose to produce ATP, CO2, and H2O
- Can also process lipids or amino acids to make ATP.
- more efficient, but takes more time
- produce 18 times more ATP
- more flexible Anaerobic (without O2)
- Does not require O2 , breaks down glucose to produce ATP and lactate.
- produces less ATP, but take fewer time
- But the ATP produced by this is too low to maintain activities for more than a few minutes.
- break down glucose into the intermediate, lactate , which can be shuttled to adjacent type I fibers to make ATP, or secreted into the blood for uptake by other tissues such as the liver to make new glucose
Muscle store a molecule called creatine phosphate. Creatine phosphate production interact to produce a continuous supply of ATP
ATP: ADP ratio declines an enzyme transfers one phosphate from one ADP to another ADP, generating one ATP and one AMP (adenosine monophosphate).
The presence of AMP triggers a switch from anaerobic respiration to aerobic respiration of blood glucose and fatty acids. If this switch were not to occur, the muscles could not maintain their activity and could ultimately fail and the body will have fatigue.
Fatigue
Temporary state of reduced work capacity Without this, muscle fibers would be worked to the point of structural damage
These mechanisms include:
- Acidosis and ATP depletion due to either an increased ATP consumption or a decreased ATP production
- Oxidative stress , which is characterized by the buildup of excess reactive oxygen species (ROS; free radicals)
- Local inflammatory reactions
Effect of Fiber Type on Activity Level
Myoglobin – stores oxygen temporarily Hypertrophy – Enlargement of muscle fibers due to: Increases the blood supply to muscles, the number of mitochondria per muscle fiber, and the number of myofibrils and myofilaments. Satellite cells – undifferentiated cells just below the endomysium Types of Muscle Contractions: Isometric (equal distance) contraction - increase the tension in the muscle without changing its length. Isotonic (equal tension) contractions have a constant amount of tension while decreasing the length of the muscle. o Concentric contractions muscle tension increases as the muscle shortens. o Eccentric contractions tension is maintained in a muscle, but the opposing resistance causes the muscle to lengthen Muscle Tone constant tension produced by body muscles over long periods of time Responsible for keeping the back and legs straight, the head in an upright position, and the abdomen from bulging.
7.4 SMOOTH MUSCLE AND CARDIAC MUSCLE
Smooth muscle
- small and spindle-shaped
- one nucleus per cell
- contain less actin and myosin than do skeletal muscle cells
- myofilaments are not organized into sarcomeres; organized to form layers
- not striated
- contract more slowly than skeletal muscles
- do not develop an oxygen deficit
- Autorhythmicity – periodic spontaneous contraction of smooth muscle
- under involuntary control
- Gap junctions – specialized cell-to-cell contacts
Cardiac muscle
- long, striated, and branching
- one nucleus per cell
- organized into sarcomeres
- distribution of myofilaments is not as uniform
- striated
- Autorhythmic – cardiac muscle contraction
- Exhibits limited anaerobic respiration.
- Intercalated disks – connects cardiac muscle cells together; allow action potentials to be conducted directly from cell to cell
7.5 SKELETAL MUSCLE ANATOMY
General Principles
Tendon – Connects muscle to bone Aponeuroses – are broad, sheet like tendons Retinaculum – band of connective tissue that holds down the tendons at each wrist and ankle Origin – most stationary, or fixed Insertion – end of the muscle attached to the bone undergoing the greatest movement. Belly – between the origin and the insertion Synergists – Members of a group of muscles working together Agonists – single muscle or group of muscles
Antagonists – opposed the activity of agonists Prime mover – plays the major role Fixators – muscles that hold one bone in place
Nomenclature
- Location
- Size - longus (long), brevis (short)
- Shape - deltoid (triangular), teres (round)
- Orientation of fascicles - rectus (straight, parallel) Circular Fascicles arranged in a circle around an opening Convergent broadly distributed fascicles converge at a single tendon Parallel Fascicles lie parallel to one another and to the long axis of the muscle Pennate Fascicles originate from a tendon that runs the length of the entire muscle. Three different patterns. Unipennate Fascicles on only one side of the tendon Bipennate Fascicles on both sides of the tendon Multipennate Fascicles arranged at many places around the central tendon. Fusiform Fascicles lie parallel to long axis of muscle. Belly of muscle is larger in diameter than ends.
- Origin and insertion - arm (brachium)
- Number of heads – two heads (bi-)
- Function – depend on function
Muscles of the Head and Neck
Facial Expression Buccinators – walls of the cheeks Depressor anguli oris – “ Frowning and pouting ” Levator labii superioris – “ Sneering ” Occipitofrontalis – raises the eyebrows Orbicularis oculi – close the eyelids Orbicularis oris – close, purses, kissing Zygomaticus – “ smiling ”
Trunk Muscles
Muscles Moving the Vertebral Column
Erector spinae – responsible for keeping the back straight and the body erect Deep back muscles – responsible for several movements of the vertebral column, including extension, lateral flexion, and rotation. RICE (rest, ice, compression, and elevation)
Thoracic Muscles
Involved almost entirely in the process of breathing
External intercostal – elevate the ribs during inspiration Internal intercostal – depress the ribs during forced expiration Diaphragm – inspiration (contracts and flattened, volume increase)
Abdominal Wall Muscles
Linea alba – consists of white connective tissue Rectus abdominis – located at each side of Linea alba Superficial to deep , these muscles are the: External abdominal oblique Internal abdominal oblique Transversus abdominis
Pelvic Floor and Perineal Muscles
Pelvic floor – formed by levator ani Perineum – inferior to the pelvic floor
Upper Limb Muscles
The muscles of the upper limb include those that attach the limb and pectoral girdle to the body and those in the arm, forearm, and hand.
Scapular Movements
Trapezius, the levator scapulae, rhomboids, serratus anterior, and the pectoralis minor.
Arm Movements
Deltoid Latissimus dorsi Pectoralis major Teres major Rotator Cuff
Lower Limb Muscles
Thigh Movements
Leg Movements
Hamstring muscles - posterior thigh muscles
Ankle and Toe Movements
7.6 EFFECTS OF AGING ON SKELETAL MUSCLE
Reduction in muscle mass Slower response time for muscle contraction Reduction in stamina Increased recovery time Begins at the age of 25 By age 80 the muscle mass has been reduced by approximately 50%. Weight-lifting exercises can help slow the loss of muscle mass Fast-twitch muscle fibers decrease in number more rapidly than slow-twitch fibers. Neuromuscular junction’s surface area decreases The number of motor neurons also decreases
REPRESENTATIVE DISEASES AND DISORDERS: Muscular System
Duchenne Muscular Dystrophy
Weakness in muscle that starts in the pelvic girdle After 3-5 years it will also involve the shoulder girdle Contractures – inflexible muscles In 10-12 years DMD patients will be unable to walk And few live beyond age of 20 Dystrophin – protein that is produces by DMD gene. In DMD patient this protein in non- functional.
Cramps
Painful, spastic contractions of a muscle; usually due to a buildup of lactic acid
Fibromyalgia
Non-life-threatening, chronic, widespread pain in muscles with no known cure; also known as chronic muscle pain syndrome
Hypertrophy
Enlargement of a muscle due to an increased number of myofibrils, as occurs with increased muscle use
Myotonic muscular dystrophy
Muscles are weak and fail to relax following forceful contractions
Tendinitis
Inflammation of a tendon or its attachment point, due to overuse of the muscle
Chapter 8 Nervous System
8.1 FUNCTIONS OF THE NERVOUS SYSTEM
- Receiving sensory input.
- Integrating information.
- Controlling muscles and glands
- Maintaining homeostasis.
- Establishing and maintaining mental activity.
8.2 DIVISIONS OF THE NERVOUS SYSTEM
Central nervous system (CNS)
Brain and Spinal cord Motor neurons - transmit action potentials from the CNS to PNS
Peripheral nervous system (PNS)
Nerves and Ganglia Enteric nervous system (ENS ) - unique subdivision of the PNS Divided into: ANS (Autonomic ) o Sympathetic (Fight or flight)
Organization of Nervous Tissue
Gray matter
Neuron cell bodies and their dendrites Cortex – gray matter in CNS; nuclei Ganglion – gray matter in PNS
White matter
Bundles of parallel axons with their myelin sheaths Nerve tracts – white matter in CNS Nerves – Bundles of axon with connective tissues in PNS
8.4 ELECTRICAL SIGNALS AND NEURAL PATHWAYS
Resting Membrane Potential
Polarized - uneven distribution of charge Generated by three main factors: (1) A higher concentration of K+ immediately inside the cell membrane, (2) A higher concentration of Na+ immediately outside the cell membrane, and (3) Greater permeability of the cell membrane to K+ than to Na+ Channels: Leak channels – always open Gated channels – closed until opened by specific signals. Chemically gated channels – opened by neurotransmitters or other chemicals Voltage-gated channels – opened by a change in membrane potential Sodium-potassium pump – Maintain the uneven distribution of Na+ and K+
Action Potentials
Local current
- movement of Na+
- Causes the inside of the cell membrane to become positive, a change called depolarization.
Depolarization
- Results Local Potential (LP)
- If not strong enough, Na receptors closes again and LP disappears
- If strong enough, Na enters the cell and LP will reach THRESHOLD value
- Threshold value – causes voltage gated Na+ channel to open Repolarization
- outward flow of K+ repolarizes the cell to its RMP
- At the end of repolarization, the charge on the cell membrane briefly becomes more negative than the resting membrane potential, hyperpolarization Action potential
- Depolarization and repolarization constitute this.
- occur in an all-or-none fashion
- If threshold is reached, an action potential occurs; if the threshold is not reached, no action potential occurs. Summary
- RMP is set by the activity of the leak channels. On stimulation, chemically gated channels are opened and initiate local potentials. If sufficiently strong, the local potentials activate voltage- gated channels to initiate an action potential. Type of action potential conduction Continuous conduction ( Unmyelinated )
- action potential is conducted along the entire axon cell membrane Salutatory conduction ( Myelinated ) – action potentials “ jump ” from one node of Ranvier to the next along the length of the axon.
The Synapse
Junction where the axon of one neuron interacts with another neuron or with cells of an effector organ
Presynaptic terminal – end of the axon Postsynaptic membrane – membrane of the dendrite or effector cell.
Synaptic cleft – space separating the presynaptic and postsynaptic membranes Neurotransmitters – Chemical substances that are stored in synaptic vesicles at presynaptic Acetylcholine (ACh)
- CNS synapses, ANS synapses, and neuromuscular junctions
- Excitatory or inhibitory
- Alzheimer disease, Myasthenia gravis
- Acetylcholinesterase – enzyme that breaks down the acetylcholine Norepinephrine
- Selected CNS synapses and some ANS synapses
- Excitatory
- Cocaine and amphetamines Serotonin
- CNS synapses
- Generally inhibitory
- Schizophrenia Dopamine
- Selected CNS synapses and some ANS synapses
- Excitatory or inhibitory
- Parkinson disease (Gamma)-aminobutyric acid (GABA)
- CNS synapses
- Inhibitory
- Drugs that increase GABA function have been used to treat epilepsy Glycine
- CNS synapses
- Inhibitory
- poison strychnine Endorphins
- Descending pain pathways
- Inhibitory
- Morphine and heroin bind to endorphin receptors
Reflexes
An involuntary reaction in response to a stimulus applied to the periphery and transmitted to the CNS.
Reflex arc – neuronal pathway by which a reflex occurs.
Simplest reflex arcs don’t involve interneurons. Five basic components: (1) Sensory receptor (2) Sensory neuron (3) In some reflexes , interneurons , which are neurons located between and communicating with two other neurons (4) Motor neuron (5) Effector organ (muscles or glands).
Neuronal Pathways
Converging pathway
- 2 to 1
- Two or more neurons synapse with the same postsynaptic neuron Diverging pathway
- 1 to 2
- One neuron divides and synapses with more than one other postsynaptic neuron
Summation – many presynaptic action potentials are needed in a process
Spatial summation
- when the local potentials originate from different locations Temporal summation
- Occurs when local potentials overlap in time.
8.5 CENTRAL AND PERIPHERAL NERVOUS SYSTEMS
The PNS collects information from numerous sources both inside and on the surface of the body and relays it by way of sensory neurons to the CNS, where one of three results is possible :
**1. The information is ignored
- Triggers a reflex
- Evaluated more extensively.** Motor neurons in the PNS relay information from the CNS to muscles and glands in various parts of the body, regulating activity in those structures.
- Tibial nerve posterior thigh muscles, the anterior and posterior leg muscles, and most of the intrinsic foot muscles.
- Common fibular nerve lateral thigh and leg and some intrinsic foot muscles.
- Sciatic nerve – bound the tibial and common fibular nerves
8.8 BRAIN
Brainstem
Connects the spinal cord to the remainder of the brain
Medulla Oblongata
- most inferior portion of the brainstem
- Regulate heart rate and blood vessel diameter, breathing, swallowing, vomiting, coughing, sneezing, balance, and coordination.
- Pyramids - two prominent enlargements Pons
- superior to the medulla oblongata
- Chewing and salivation. Midbrain
- superior to the pons
- smallest region of the brainstem
- Colliculi – 4 mounds Two inferior colliculi – auditory nerve pathways in the CNS Two superior colliculi – involved in visual reflexes and receive touch and auditory input
- Substantia nigra – regulate general body movements Reticular Formation
- A group of nuclei collectively
- Reticular activating system – Important in arousing and maintaining consciousness and in regulating the sleep-wake cycle
- Removal of visual or auditory stimuli may lead to drowsiness or sleep.
Cerebellum
Little brain attached to the brainstem by cerebellar peduncles Act as a comparator Learning motor skills
Diencephalon
Thalamus
Largest part of the diencephalon Interthalamic adhesion – connects thalamus at the center Influences mood and registers an unlocalized, uncomfortable perception of pain.
Epithalamus
Small area superior and posterior to the thalamus Involved in the emotional and visceral response to odors, and the pineal gland Pineal gland – endocrine gland that may influence the onset of puberty
Hypothalamus
most inferior part of the diencephalon Control of body temperature, hunger, and thirst. Sensations such as sexual pleasure, rage, fear, and relaxation after a meal are related to hypothalamic functions. Nervous perspiration – Emotional responses that seem inappropriate to the circumstances Emotional eating Infundibulum – ex tends from the floor of the hypothalamus to the pituitary gland Controlling the secretion of hormones from the pituitary gland. Mammillary body – emotional responses to odors and in memory
Cerebrum
largest part of the brain Longitudinal fissure – divide the cerebrum into left and right hemispheres
Gyri – numerous folds Sulci – intervening grooves Frontal lobe
- Voluntary motor functions, motivation, aggression, mood, and olfactory (smell) reception. Parietal lobe
- Center for receiving and consciously perceiving most sensory information, such as touch, pain, temperature, and balance. Central sulcus – Separate frontal and parietal lobes Occipital lobe
- receiving and perceiving visual input Temporal lobe
- Olfactory ( smell ) and auditory ( hearing ) sensations and plays an important role in memory.
- Psychic cortex - abstract thought and judgment. ( anterior and inferior )
- Lateral fissure – separate temporal lobe from the other lobes
- Insula (or fifth lobe) – within the fissure
8.9 SENSORY FUNCTIONS
Sensory input to the brainstem and diencephalon helps maintain homeostasis. Input to the cerebrum and cerebellum keeps us informed about our environment and allow the CNS to control motor functions. A small portion of the sensory input results in perception , the conscious awareness of stimuli
Ascending Tracts
from the periphery to various parts of the brain Usually begin with the prefix spino- (indicating that they begin in the spinal cord.) Two examples of ascending tracts : Spinothalamic tract
- Transmits action potentials dealing with pain and temperature to the thalamus and on to the cerebral cortex.
Dorsal column
- transmits action potentials dealing with touch, position, and pressure Spinocerebellar tracts
- transmit information about body position to the cerebellum
Sensory Areas of the Cerebral Cortex
Primary sensory areas
- Where sensations are perceived Primary somatic sensory cortex
- General sensory area
- Located in the parietal lobe posterior to the central sulcus. Association areas
- involved in the process of recognition
8.10 SOMATIC MOTOR FUNCTIONS
Involuntary movements – occur without conscious thoughts Voluntary – consciously activated Upper motor neurons – have cell bodies in the cerebral cortex Lower motor neurons – cell bodies in the anterior horn of the spinal cord gray matter or in cranial nerve nuclei.
Motor Areas of the Cerebral Cortex
Primary motor cortex – located in the posterior portion of the frontal lobe, directly anterior to the central sulcus. control voluntary movements of skeletal muscles Premotor area of the frontal lobe – where motor functions are organized before they are actually initiated in the primary motor cortex.
