chapter 13 - neuronal communication Flashcards
what is homeostasis
maintaining relatively constant internal environment
what is cell signalling
communication of cells
what signal is used between neurones and synapes
neurotransmitter
what signal is used between large distances
hormones
what is a stimulus
changes in internal and external environment
what are neurones
specialised nerve cells
what are the features of neurones
cell body
dendrons
axons
what is function of cell body
has high number of endoplasmic reticulum and mitochondria to produce neurotransmitters
what is function of dendrons
short extensions from cell body to transmit electrical signals towards cell body
what is function of axons
singular elongated nerve fibres that transmit impulses away from cell body
what is a sensory neurone
transmit impulses from sensory receptor cells to a relay neurone, motor neurone or brain
Have one axon and one dendron
what are relay neurones
transmit impulses between neurones
have many short axons and dendrons
what are motor neurones
transmit impulses from relay neurone or sensory neurone to effector
have one long axon and many short dendrites
what is myelin sheath made of
schwann cells produce layers of plasma membrane around axon
what does myelin sheath do
acts as insulating layer so myelinated neurones to conduct electrical impulse at faster speed
what is a node of ranvier
gaps between schwann cells so electrical impulses jump from one node to next as it travels along neurone
what are the features of a sensory receptor
specific to a single type of stimulus
act as transducer- convert stimulus to nerve impulse
what are the features of a sensory receptor
specific to a single type of stimulus
act as transducer- convert stimulus to nerve impulse
what are 4 types of sensory receptors
mechanoreceptor
chemoreceptor
thermoreceptor
photoreceptor
what is pacinian corpuscles
specific sensory receptor that detected mechanical pressure in skin
how does pacinian corpuscle convert mechanical pressure into nervous impulse
1) in resting state, stretch mediated sodium ions channels are closed
2) when pressure is applied, corpuscle changes shape causing membrane of neursone to stretch
3) sodium ion channels open so sodium ions diffuse in depolarising the membrane resulting in generator potential
5) generator potenital creates an action potential that passes along sensory neurone
what is resting potential in axon
inside of membrane is more negative than outside so is polarised ( -70mV)
how is resting potential created
sodium ions are actively transported out of axon whereas potassium ions are actively transported into axon by specific intristic protein ( sodium potassium pump). 3 sodium move out and 2 potassium move in
sodium diffuse back into axon down electrochemical gradient and potassium ion diffuse out but most sodium gated ion channels are closed so inside becomes negative
what happens during action potential
1) neurone has resting potential
2) stimulus trigger ssome sodium voltage gated ion channels to open making membrane more permabel to sodium ions
sodium io0ns diffuse inside neurone making it less negative cuasing even more sodium ion channels to op0en ( positive feedbacj) . At 40 mV voltage sodium ion channels close so inside becomes more negative as potassium moves out
more potassium diffuse out causoing hyperpolarisation
then potassium volatgae channel close repolarising neurone
what is saltatory conduction
action potential jumping from one node to one node faster than wave of depolarisation which needs ATP for repolarisation
what factors affect speed of action potential
myelination
axon diameter - the bigger the diameter, fatser the impulse as there is less resistance in flow of ions in cytoplasm
temperature
what is all or nothing
a certain threshold value will always trigger same sized action potential response no matter how big the stimulus
only affects frequency
what is a synapse
junction between 2 neurones
how is synaptic knob adapted to its function
swollen end of presynaptic neurone
contains many mitochondria and large amounts of ER to create neurotransmitters
what is excitatory neurotransmitter
result in depolarisation of post synaptic neurone
creates action potential is threshold is reached
e.g. acetylcholine
what is inhibitory neurotransmitter
result in hyperpolarisaton of postsynaptic membrane
prevents action potential
E.G. GABA
how are impulses transmitted across synapses?
1) action potential at end of presynaptic neurone causes depolarisation which cause calcium ion channels to open
2)calcium ions diffuse into presynaptic knob
3)calcium ions cuase synaptic vesicles to fuse with presynaptic membrane releasing neurotransmitter into synaptic cleft by exocytosis
4) neurotransmitter diffuses across synaptic cleft and binds with specific receptor molecule on postsynaptic membrane causing sodium ion channels to open
5) sodium ions diffuse into postsynaptic neurone triggering action potenital and impulse is propagated along postsynaptic neurone
what is the role of synapses
1) ensure impulses are unidirectional as neurotransmitter receptors are only at postsynaptic membrane
2) allow an impulse from one neurone to a number of neurons at multiple synapses to create different responses
3) a number of neurones may feed in same synapse with single postsynaptic neurone
what is spatial summation
when many presynaptic neurones connect to one postsynaptic neurone each releasing neurotransmiter
what is temporal summation
when a single presynaptic neurone releases neurotransmitters serveral times
what does central nervous system consist of
brain and spinal chord
what does peripheral nervous system consist of
neurones that connect CNS to rest of body
sensory neurones that carry nerve impulses from receptors to CNS
motor neurones that carry nerve impulses from CNS to effectors
what is somatic nervous system
part of peripheral nervous system
under concious control
what is autonomic nervous system
works constantly
under unconscious control
involuntary
what is sympathetic nervous system
part of autonomic nervous sytem
increases activity
what is parasympathetic nervous system
decreases activity
what protective membrane surrounds the brain
meninges
what is cerebrum
controls voluntary controls like learning , memory, personality and conscious thought
what is cerebellum
controls unconscious functions such as posture and balance
what is medulla oblongata
used in autonomic control like controlling heart rate and breathing rate
what is hypothalamus
regulatory centre for temperature and water balance
what is pituitary gland
stores and releases hormones that regulate body functions
what are functions of hypothalamus
-controls complex patterns of behaviour like sleeping and feeding
- monitor composition of blood plasma
- produce hormones as it is an endocrine gland
what is the anterior pituitary( front)
produces 6 hormones such as FSH
what is posterior pituitary ( back)
stores and releases hormones produced by hypothalamus such as ADH
what is a skeletal muscle
responsible for movement
voluntary
what is cardiac muscle
found in heart
myogenic
what is smooth muscle
involuntary
found in walls of organs like stomach
found in walls of blood vessels and digestive track
what are muscle fibres made of
sacrolemma ( plasma membrane)
nuclei
sarcoplasm
t-tubules
lots of mitochondria
sarcoplasmic reticulum
myofibrils containing actin and myosin
what is z-line
contains actin
distance between 2 z-lines is sacromere
what is Heavy zone
only myosin present
lighter band
what is A zone
myosin and areas where myosin and actin overlaps
dark bands
what happens during contraction
myosin filaments pull actin filaments closer towards centre of sarcomere resulting in light band becoming narrower, z - lines moving closer shortening sarcromere, h -zone becoming narrower
what is the structure of myosin
globular heads that are hinged which allows them to move back and forwards
head has binding site for actin and ATP
what is the structure of actin
has binding site for myosin heads
binding sites blocked by tropomysosin held in place by troponin
how is tropomyosin removed from blocking binding site in actin
1) action potential reaches neuromuscular junction and stimulates calcium ion channels to open diffusing in
2) calcium ions in synaptic knob cause synaptic vesicles to fuse with presynaptic membrane
3) acetylcholine is released into synaptic cleft by exocytosis and diffuses across synapse which binds to receptors on postsynaptic membrane ( sarcolemma) opening sodium ions channel resulting in depolarisation
4)acetylcholine broken down by acetylcholinesterase into choline and ethanoic acid preventing muscle from being overstimulated and diffuse back into neurone recombined to acetylcholine using atp from mitochondria
5)depolarisation of sarcolemma travel through t-tubules to sarcoplasmic reticulum stimulating it to open calcium ion channel to open which diffuse down concentration gradient to sarcoplasm
6) calcium ions bind to troponin causing it to change shape which pulls on tropomyosin away from actin-myosin binding site
7) now the actin and myosin can form acti-myosin cross bridge
what does atp do to myosin
causes myosin head to detach from actin filament
how is myosin returned to orginal position
calcium ions in sarcoplasm activates ATPase activity which hydrolyses ATP to ADP and phosphate
what are 3 sources of energy for muscles
aerobic respiration
anaerobic respiration
creatine phosphate
