Unit 3 Pathophysiology - Chapter 15 Structure and function of neurological system

Question 1

Structural nervous system

Answer 1

• central nervous system (CNS)
• peripheral nervous system (PNS)

Question 2

Functional nervous system

Answer 2

• somatic nervous system (SNS)
• autonomic nervous system (ANS)

Question 3

CNS

Answer 3

brain and spinal cord

Question 4

PNS

Answer 4

cranial and spinal nerves that carry impulses twoard CNS (afferent and away from the CNS (efferent) to target organs or skeletal muscles

Question 5

Somatic nervous system

Answer 5

• motor and sensory pathways for voluntary motor control of skeletal muscle

Question 6

ANS

Answer 6

motor and sensory involuntary control of organ systems

Question 7

Nervous tissue?

Answer 7

• neuron and neuroglial cells
• neuron - transmit/receive electrical and chemical impulses
• neuroglial cell — supportive functions

Question 8

Neuron

Answer 8

• cell body
• one or more dendrites
• an axon (myelin sheath around selected axons form insulation that allows quicker nerve impulse conduction => saltatory conduction)
• 3 types of neurons (sensory, associatioinal, and motor
• unipolar (single axon and nothing else, mostly invertebraes - such as flies), pseudounipolar (axon split into two brances – most sensory neurons), bipolar (extends out to one axon and the other is one dendrite, with cell body in middle, sensory [smell, sight, taste, hearing, touch, balance, proprioception]), and multipolar (single axon and symmetrical dendrites that extend from it – most common neuron in CNS)

Question 9

Neuroglial cells

Answer 9

• nerve glue
• support CNS and comprise approximately half of total braine and spinal cord volume

Question 10

Nerve injury in peripheral and CNS neurons

Answer 10

• cause axonal reaction
• includes local, antegrade refers to moving or extending forward as opposed to retrograde which implies moving backward or opposite to the direction of flow.
• resultant neuronal swelling => Chromatolysis is a reactive change that occurs in the cell body of damaged neurons, involving the dispersal and redistribution of Nissl substance (rough endoplasmic reticulum and polyribosomes) in order to meet an increased demand for protein synthesis such as is required to regenerate axons.
• CNS neuron injury usually l/t permanent loss of fx

Question 11

Synapse

Answer 11

• region between adjacent neurons
• for neuron and muscle, its called myoneural junction

Question 12

Nerve impulse predominantly regulated by

Answer 12

• EPSP stands for excitatory post-synaptic potential and IPSP stands for inhibitory post-synaptic potential. In simple terms, EPSP creates an excitable state at the post-synaptic membrane that has the potential to fire an action potential whilst IPSP creates a less excitable state that inhibits the firing of an action potential by the post-synaptic membrane.
• temporal (converts a rapid series of weak pulses from a single source into one large signal) and spatial (several weak signals from different locations are converted into a single larger one) summation
• convergence (a neuron receives input from nay neurons in a network)
• divergence (one neuron communicate with many other neurons in a network)

Question 13

Brain consists of (3)?

Answer 13

1. forebrain
2. midbrain
3. hindbrain

Question 14

Forebrain

Answer 14

• telencephalon (two cerebral hemispheres) includes cerebral cortex and basal ganglia
• forebrain top half, then mid and hindbrain
• important for conscious perception of internal/external stiimuli, cognition, and memory processes + voluntary control of skeletal muscles
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• Posterior portion of forebrain (diencephalon) — includes thalamus, hypothalamus, epithalamus + subthalamus
• fx includes: sensory information, autonomic fx, links to limbic system for memory and emotion
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• Precentral gyrus (frontal lobe [towards back of lobe]) —- center for voluntary control of skeletal muscle
• Postcentral (parietal lobe [middle]) —- center for sensory perception
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• broca area (anterior to postcentral gyrus located in parietal lobe, side of frontal lobe) —- ability to speak words
• wernicke’s area (at postcentral gyrus in parietal lobe (side) right above temporal lobe) —- ability to understand word meanings

Question 15

Midbrain

Answer 15

• below hypothalamus (connecting w/ pons then medulla)
• relay ceneter for some motor/sensory trtacts; auditory and visual reflex center, temperature control, sleep-wake cycles, arousal, and attention

Question 16

Hindbrain

Answer 16

• metenecephalon (cerebellum and pons)
• myelencephalon (medulla oblongata)
• cerebellum and pons => coordination and refinement of skeletal muscle mvmt
• medulla controls HR, blood pressure, reflex activities (swallowing coughing and vomiting)
• ascending reticular formation (brain stem, wakefulness + attention)

Question 17

Spinal cord

Answer 17

• nerve fibers that connect to brain w/ periphery
• cervical thoracic, lumbar, and sacral regions
• gray matter (cell bodies) of spinal cord divided into horns
  1) anterior (lower motor neurons) - ventral
  2) posterior (sensory neurons) - dorsal
  3) lateral horns (autonomic neurons)
• white matter similar division (posterior, lateral, and anterior columns)

ascending tracts found in all columns (sensory)
descending tracts (motor) found in lateral and anterior columns
reflex arcs are completed in spinal cord and influenced by higher centers

Question 18

Major motor tracts

Answer 18

• corticobulbar tract (conducts impulses from the brain to the cranial nerves) – synapses on motor cranial nuclei within the brainstem and provides voluntary control of muscles in the head and neck, including face.
• lateral corticospinal (conducts impulses from the brain to the spinal cord - The primary responsibility of the lateral corticospinal tract is to control the voluntary movement of contralateral limbs)
• anterior corticospinal (movement of the muscles of the trunk, neck, and shoulders.)
• Extrapyramidal tracts: Originate in the brainstem, carrying motor fibres to the spinal cord. They are responsible for the unconscious, reflexive or responsive control of musculature, eg muscle tone, balance, posture and locomotion. The reticulospinal tract modulates motor movement by inhibiting and exciting spinal activity [locomotion and postural control] (descending pathway). While vestibulospinal tract comes from a vestibular nucleus in the pons and causes extensor mucles of the body to rapidly contract (best witnessed when a person starts to fall backward). Rubrospinal tract originates in red nucleus, decussates, and terminates in the cervical spinal - important for muscle movement and fine muscle control in upper extremities.
• The pyramidal tract, especially the corticospinal tract, plays a significant role in controlling voluntary muscular movements

Question 19

Major sensory pathways

Answer 19

Posterior column
* carries fine touch (2 pt discrimination), vibration, and proprioceptive information – self-movement, force, and body position (epicritic information)
* 3-neuron chain

spinothalamic tract (anterior and lateral)
* vague touch and pian, including temperature perception
* 3-neuron chain?
* protopathic - relating to a sensory nerve that perceives only coarse stimuli, such as pain

spinocerebellar tract
* somatosensory part of the sensory nervous system that relays unconscious proprioceptive information from the lower limbs and trunk of the body to the cerebellum

Question 20

CNS protected by?

Answer 20

• Scalp
• Bony cranium
• meninges (Meninges are three layers of membranes that cover and protect your brain and spinal cord (your central nervous system [CNS]). They’re known as: Dura mater: This is the outer layer, closest to your skull. Arachnoid mater: This is the middle layer. Pia mater: This is the inner layer, closest to your brain tissue.)
• vetebral column (The bones, muscles, tendons, and other tissues that reach from the base of the skull to the tailbone)
• CSF (cerebrospinal fluid) — formed from blood components in the choroid plexuses (network of blood vessels) of the ventricles and is reabsorbed in the arachnoid villi (located in the dural venous sinuses [group of sinuses or blood channels that drains venous blood circulating from the cranial cavity found betwen endosteal and meningeal layers of dura mater]) after circulating through the brain and spinal cord.
• (continued) CSF can cushion brain and spinal cord from injury + provide nutrients

Question 21

Circle of willis

Answer 21

• encircles the stalk of the pituitary gland and provides important communications between the blood supply of the forebrain and hindbrain
• paired carotid and vertebral arteries supply blood to brain and connect to form the circle of Willis
• Major brances projecting from circle are anterior, middle, and posterior cerebral arteries
• Drainage of blood from brain => venous sinuses and jugular veins

Question 22

Blood supply to spinal cord

Answer 22

• vertebral arteries and branches arising from aorta

Question 23

blood-brain barrier

Answer 23

• composed of endothelial cells in brain capillaries
• plus associated supporting cells
• prevents harmful substances from entering brain

Question 24

PNS function

Answer 24

relays info from CNS to muscle and effector organs through cranial and spinal nerve tracts arranged in fasicles bound together to form peripheral nerve

• 31 pairs of spinal nerves contain sensory and motor neurons

Question 25

ANS and aging

Answer 25

• decreased number of neurons, lower brain weight and sizes
• decreaed myelin
• deposit of lipofuscin (yellow-brown pigment)
• neuritic (amyloid) plaques (consist of deteriorating neuronal material surrounding deposits of a sticky protein called amyloid beta. In human disease: Alzheimer’s disease. … patients with Alzheimer’s disease are neuritic plaques and neurofibrillary tangles), multiple neurofibrillary tangles (collection of protein called tau that collect inside neurons), and lewy bodies (abnormal deposits of a protein called alpha-synuclein in the brain) common w/ change
• Cerebral atherosclerosis, decreased vascular density, increased blood-brain barrier permeability
• Diminishes sensory fx, sleep disturbances, and memory impairments