Nervous System

Question 1

roles

Answer 1

monitors internal and external environments
integrates sensory information
coordinates voluntary and involuntary responses of many other organ systems
performed by neurons which are protected by neurologia

Question 2

receptors

Answer 2

mechanoreceptors- respond to mechanical pressure or distortion
chemoreceptors- respond to chemical changes
photorecpetors- respond to light
thermoreceptors- sense changes in temperature

Question 3

structure

Answer 3

CNS- brain and spinal cord
integrates and coodrinates the processing of sensory data and transmission of motor commands

PNS- includes all neural tissue outside CNS
delivers sensory info to cns

Question 4

divisions

Answer 4

afferent - sensory commands, coming back to CNS
efferent - motor commands, moving away from CNS (includes somatic and autonomic- parasymp and symp)

Question 5

anaxonic neurons

Answer 5

found in brain and special sense organ- pass info between other neurons
very small
no anatomic features that distinguish dendrites from axon
functions poorly understood

Question 6

structure of neuron

Answer 6

cell body- nucleus, mitochondria, golgi
dendrites extending from cell body
axon hillock- origin of action potential
myelin sheath- surrounds axon
nodes of ranvier- gaps between sheath
axon- action potential travels down
axon terminals synapse with dendrites of next neuron

Question 7

bipolar neuron

Answer 7

have 2 processes- 1 dendrite and 1 axon with cell body between them
rare
occur in special sense organ eg sight, hearing etc

Question 8

unipolar

Answer 8

dendrites and axon are continuous, cell body lies off to one side
most sensory neurons of PNS are unipolar

Question 9

multipolar

Answer 9

has 2 or more dendrites and a single axon
most common neurons in CNS
all motor neurons that control skeletal muscle are multipolar

Question 10

spinal cord

Answer 10

major passageway of sensory and motor impulses to/from the brain
integrated info on its own and controls spinal reflexes and automatic motor responses
white matter- motor neurons (myelinated)
grey matter-interneurons (unmyelinated)

Question 11

spinal cord structure

Answer 11

consists of 31 segments- each containing a pair of dorsal root ganglia containing cell bodies of sensory neurons
dorsal roots bring sensory information to spinal cord

pair of ventral roots contains axons of motor neurons
d + v roots are bound together into a single spinal nerve

Question 12

sectional anatomy of spinal cord

Answer 12

gray matter contains cell bodies and neuroglia cells
white matter contains myelinated and unmyelinated axons

Question 13

spinal nerves

Answer 13

31 pairs of spinal nerves are grouped according to the region of vertebral column from which they originate
each pair of spinal nerves monitors a specific region of the body surface known as a dermotome
damage of the spinal nerve or of dorsal root ganglia produces a characteristic loss of sensation in the corresponding region of the skin

Question 14

reflex arc

Answer 14

arrival of stimulus and activation of receptor
activation of a sensory neuron
information processing in CNS
activation of a motor neuron
response by a peripheral effector

withdrawal reflex- may involve other parts of the body too

Question 15

parts of brain

Answer 15

reptilian brain- brain stem
mamallian brain- limbic system (feelings, social interactions)
higher brain- decision making, ethics etc, separating us from other species
20% of energy expenditure only 3% of body mass

Question 16

6 regions of brain

Answer 16

cerebrum
cerebellum
diencephalon
mesencephalon
pons
medulla oblangata

Question 17

lobes - cerebrum

Answer 17

frontal- voluntary motor activity, speech, elaboration of thoughts
somatic motor association
temporal- initial reception of auditory info
auditory association
occipital- initial processing of visual info
visual association
parietal- receiving and processing sensory info
somotic sensory association

Question 18

cerebellum

Answer 18

cortex and nuclei- involuntary coordination and control of ongoing body movements
cerbelllar peduncles- link regions of the brain, integration and communication
affected by alcohol which affects balance

Question 19

diencephalon

Answer 19

contains thalamus, epithalamus, hypothalamus, pituitary gland, pineal gland
hypothalamus- controls emotion

Question 20

mesenchephalon (midbrain)

Answer 20

processes audio and visual data- links to temporal and occipital lobe
maintenance of consciousness

Question 21

pons

Answer 21

links cerebellum with mesencephalon, diencephalon, cerebrum and spinal cord
involved in control of respiration- pace and depth of breathing

Question 22

medulla oblangata

Answer 22

link between brain stem and spinal cord
relaying sensory info to brain stem and soinal cord
autonomic regulation of visceral functions- organs eg control of heart

Question 23

brain protection and support

Answer 23

physical protection- bones of the cranium, cranial meninges, cerebrospinal fluid

biochemical isolation- blood brain barrier- isolation of circulation through variation in permeability of CNS capillaries

Question 24

cranial meninges

Answer 24

layers of membrane
3 layers- dura mater, arachnoid mater (web like structure) , pia mater
protects brain from cranial trauma

Question 25

cerebrospinal fluid

Answer 25

surrounds exposed surfaces of CNS interchanges with interstitial fluid of brain functions- cushion, support, transport of nutrients and chemical messengers and waste products

Question 26

cell membrane potential

Answer 26

uneven distribution of charges known as potential difference PD across cell membrane called membrane potential resting potential -70mV (very small)-(-ve =polarised)

Question 27

ions in membrane

Answer 27

outside cell= high conc of Na+ and Cl- inside cell= high conc of K+ and negatively charged proteins Pr- membrane has selective permeability which maintains intra vs extracellular fluid differences ions can enter or leave the cell with help from channel and carrier proteins

Question 28

resting potential

Answer 28

membrane contains different types of channels- leak and gated leak= always open gated= open/close depending on circumstances

Question 29

passive movement

Answer 29

chemical conc gradient- K+ moved out of the cell and Na+ into cell K+ moves out of cell faster than Na+ can move into cell electrical gradient- +ve charged outer membrane surface repels +ve K+ ions -ve charge inner membrane attracts +ve Na+ chemical gradient is stronger than electric repelling force

Question 30

sodium potassium pump

Answer 30

maintains resting potential at -70mV NaK+ pump- 3 intra Na+ ions exchanged for 2 extra K+ ions Na+ out and K+ in rate of Na+ entry to K+ loss is precisely balanced

Question 31

depolarisation

Answer 31

opening of gated Na+ channels increases Na+ entry into cell as +ive ions increase on the inner surface of the cell, the membrane potential shifts to 0mV this shift is called depolarisation when stimulus is removed, repolarisation occurs

Question 32

graded potentials

Answer 32

local potentials only affect a limited portion of cell membrane- cannot spread far from site of stimulation affect a small area produced by any stimulus that opens a gated channel

Question 33

graded potential

Answer 33

1- resting membrane exposed to chemical, Na+ channels open and enter, depol occurs 2- movement of Na+ produces local current, depolarises nearby cell membrane (graded- lower further away), change in potential proportional to stimulus 3-inactivation of sodium channels and activation of K+ channels 4-when stimulus is removed, membrane potential returns to normal (repol) graded potentials can influence operations in distant portions if they lead to action potentail

Question 34

action potential

Answer 34

electrical signal that affects entire membrane surface change of permeability of cell membrane skeletal muscle fibres and axons have excitable membranes that will conduct action potential begins near axon hillock generated by opening and closing of Na+ and K+ must depolarise to threshold all or none principle

Question 35

continuous propagation

Answer 35

occurs in unmylelinated axon 1- action potential in first segment depolarises membrane 2-local currents form and Na+ spread away from channel, depolarises next segment 3- second segment develops action potential and first segment enters refractory period 4- local current depol next segment and cycle repeats, action pot travels in 1 direction (1m/sec)

Question 36

saltatory propagation

Answer 36

occurs in myelinated axons- axon is wrapped in layers of myelin depolarisation only occurs at the nodes, action potential jumps from node to node faster than continuous propagation (18-140m/sec) 1-action potential at segment 2-local current produces graded depol 3-action potential develops at node 4-local current produces graded depol that brings axolemma at next node to threshold

Question 37

chemical synapse

Answer 37

synapse- site of communication between a nerve cell and other cell information transfer occurs through the release of neurotransmitters from synaptic terminal may occur on a dendrite/ cell body opposing cell membranes are separated by a space called the synaptic cleft

Question 38

neurotransmitters

Answer 38

excitatory- cause depol of PSM promote action potentials inhibitory- cause hyperpol of PSM suppress action potentials

Question 39

acetylcholine and cholinergic

Answer 39

ACh is released at cholinergic synapses