nervous system

Question 1

what is a stimulus

Answer 1

it is any change in envo tht causes an organism to react

Question 2

what is irritability?

Answer 2

it is the ability to detect n respond to changes in the envo

Question 3

what detects stimulus? what do thy do?

Answer 3

sense organs/receptors:
they help the body to adjust rapidly to any changes in the envo
they enable various parts of the body to coordinate w one anothr quickly

Question 4

involuntary vs voluntary

Answer 4

automatic & not controlled consciously vs controlled consciously

Question 5

cns( central nervous system)

Answer 5

brain + spinal cord

Question 6

peripheral nervous system(pns)

Answer 6

cranial nerves + spinal nerves-> ending of these nerves r sense organs/receptors

Question 7

fuction of the cns n pns

Answer 7

to collect info on ext n int envo-> carried out by receptors which form the sensory system

Question 8

function of receptors

Answer 8

receive stimuli
info gathered is thn conv into nerve impulses n send to cns by nerves thus helping the organism to respond quickly(such as causing effectors to contract/relax) to change in envo
cld b nerve endings or tgthr w othr cells to form a sense organ

Question 9

sensory/receptor neurone

Answer 9

transmits nerve impulses frm sense organ to cns

Question 10

axon

Answer 10

nerve fibres tht transmit nerve impulses away from cell body

Question 11

dendron

Answer 11

nerve fibres tht transmit nerve impulses to cell body

Question 12

what is a nerve?

Answer 12

a bundle of nerve fibres enclosed in a sheath of connective tissue, emerge frm brain(cranial nerve) or spinal cord(spinal nerve)

Question 13

mixed fibres

Answer 13

mix of sensory n motor nerve fibres-> like spinal nerves

Question 14

nerve fibre?

Answer 14

is a strand of cytoplasm extending frm the cell body

Question 15

synapse

Answer 15

it is a junction btwn 2 neurons or btwn a neurone & an effector-> impulses transmitted frm axon of one neurone to dendron of anothr, across a tiny space thru neurotransmitters which r chemicals released by neurones(by exercise or addiction more will b released-> if u release too much or too little it bcomes a diease n u hv to take medicine to control the amt released

Question 16

relay/intermediate neurone

Answer 16

inside spinal cord n one to brain

it is the intermediate nerve tht transmits nerve impu;se frm one neuorone to anothr, found inside cns(spine+brain)

Question 17

dendrites

Answer 17

receive nerve impulses frm othr neurones

Question 18

cell body

Answer 18

contains nucleus, cytoplasn, cell surface membrance n othr organelles-> irregularly shaped

Question 19

myelin sheath

Answer 19

electrical insulator frm bioelectricity, layer of fatty substance enclosing many nerve fibres

Question 20

motor/effector neurone

Answer 20

transmits nerve impulsrs frm the cns to the effectors

Question 21

node of ranvier

Answer 21

region whr myelin sheath is absent-> nerve impulses cannot b trnasmitted thru myelin sheath so thy hv to “jump” frm one node to anothr thus speeding up the transmission of nerves

Question 22

axon terminals

Answer 22

impulses along nerve tissue transmit nerve impulses to effector

Question 23

motor end plate

Answer 23

junction btwn axon terminal n musce fivre, nerve impulses r transmitted across by chemicals which stimulate the muscles

Question 24

transverse cross section of spinal cord:

what is grey matter?

Answer 24

cell bodies of neurone which forms the outer layer of brain n central region of spinal cord

Question 25

white matter

Answer 25

consists mainly of nerve fibres, forms central parts of brain n outer layers of spinal cord

Question 26

central canal

Answer 26

contains a fluid called cerebrospinal fluid tht brings nutrients to spinal cord

Question 27

spinal nerve

Answer 27

dorsal root + ventral root joins to form it, contains both sensory n motor neurone

Question 28

dorsal root

Answer 28

contains only nerve fibres of sensory neurones tht transmit impulses to spinal cord

Question 29

ventral root

Answer 29

only nerve fibres of motor neurones tht transmit impulses to spinal cord

Question 30

dorsal root ganglion

Answer 30

small swelling in dorsal root tht contains cell bodies of sensory neurones

Question 31

relay neurone

Answer 31

transmit impulses from sensory neurones to motor neurones | relay neurones may transmit impulses frm brain, down white matter of spinal cord to grey matter(voluntary action)

Question 32

if relay neurone is cut

Answer 32

nerve implses transmitted to brain, then transported to brain but there is no way to carry out the action since it cannot trnasmit to effectors(can do so voluntarily but not reflex)

Question 33

if motor neurone is cut

Answer 33

can feel pain but cannot move hand away

Question 34

if sensory neuron is cut

Answer 34

cannot feel pain but can move hand away voluntarily

Question 35

define reflex action

Answer 35

an involuntary action which is an immediate response to a specific stimulus w/o conscious control normally performed in response to unpleasant n life-threatening stimulus

Question 36

cranial reflexes

Answer 36

controlled by brain, not conscious will n usually occur in the head region eg: pupil reflex, blinking n salivation

Question 37

spinal reflexes

Answer 37

controlled by spinal cord eg: knee jerk reflex, sudden withdrawal of hand whn touching hot obj involuntary action occurs 1st n thn only brain relaises bcos the relay neurone is shrter

Question 38

reflex action pathway

Answer 38

``` stimulus detected by RECEPTORS/SENSE ORGANS impulse sent along sensory neurone to CNS(brain + spinal cord)-> this one is in spinal cord if it is spinal reflex n its in brain if its cranial reflex synapse, relay neurone, synapse motor neurone effector(muscle or glands) response ```

Question 39

voluntary action

Answer 39

touch stimulates receptors in skin. receptors generate nerve impulses transmitted via sensory neurone to relay neurone in spinal cord relay neurone transmits nerve impulse to brain( w/o a stimulus it wld just start here) sensation of touch is felt whn impulse rchs the brain n brain interprets the pattern of nerve impulses(isit good or bad touch?) brain initiates an impulse which is transmitted by relay neurone down spinal cord to motor neurone which transmits nerve impulses to effector such as muscles in arm response intiated muscles contracts to move arm away

Question 40

so voluntary action vs reflex action:

Answer 40

va: conscious control while ra: not under conscious control va: does not occur immediately in response to stimulus ra: action is performed immediately in response to stimulus va: impulse originated frm brain( we choose to do it) ra: impulse originated frm sense organ