animal responses Flashcards
what are the two subdivisions of the human nervous system
central nervous system (CNS) - includes brain and spinal chord
and Peripheral nervous system (PNS) - includes all neurones that lie outside the CNS
what are most neurones within the CNS
relay/ intermediate neurons
how are the PNS’s axons and dendrons arranged?
in bundles / nerves
what is the autonomic nervous system responsible for?
- many homeostatic mechanisms
- controlling heightened responses (stress response)
what are nerves?
bundles containing the PNS’s axons and dendrons
what are features of autonomic neurones
- non-myelinated
- connections to effectors - consists of TWO neurones (in series)
- two neurones connected at a swelling (ganglion)
sympathetic and parasympathetic
effectors:
smooth muscle
cardiac muscle
exocrine glands
what are features of somatic neurones
myelinated
connections to effectors - consist of ONE neurone
effectors:
- voluntary/ skeletal muscle
what is the structure of sympathetic nervous system
many nerves
pre-ganglionic axons SHORT
ganglion - just outside nervous system
post-ganglionic axons LONG
what is the structure of the parasympathetic nervous system
pre-ganglionic axons - very long
ganglion - on the organ
post-ganglionic axons - very short
what is the function of the parasympathetic nervous system
return the body to rest
“rest and digest”
sympathetic nervous system
prepares the body for action
“fight or flight”
what are some examples of the effects of the sympathetic NS
- increased heart rate
- pupil dilation
- increased ventilation rate
what are some examples of the effects of the parasympathetic NS
- decreased heart rate
- pupil dilation
- decreased ventilation rate
what does the cerebrum do
all higher order processes
- thinking
- planning
- language
- memory
- emotions
what does the hypothalamus control
- control of the autonomic nervous system
- control of some endocrine glands
what are the main features of the cerebrum
- largest part of the human brain
- divided into cerebral hemispheres (right and left)
2 hemispheres are linked by the corpus callosum (white matter) - highly developed in humans
outer layer = cerebral cortex (grey matter)
what does the medulla oblongata control?
control of breathing
heart rate
smooth muscle
what does the medulla oblongata contain
- respiration centre
- cardiac centre
how does the hypothalamus bring about responses
- through the autonomic nervous system
- through controlling secretions of the pituitary gland
what are features of reflex actions
- do not involve any processing
- short nervous pathway
- two/three neurones - sensory, motor and sometimes relay
- brain may be involved after action has happened
- survival value
- danger
describe the knee jerk reflex
- spinal reflex - passes through the spinal chord
- only two neurones involved (sensory and motor)
- no relay so can’t be inhibited
- quicker helps with coordinated movement and balance
what physiological changes might occur during a fight or flight response
- blood pressure increases
- vasodilation
- increased blood glucose concentration (more glycogenolysis)
how are fight or flight responses coordinated
by the hypothalamus
- activates sympathetic NS - activates adrenal medulla
- secretion of adrenaline into blood stream
and
sympathetic nervous system
impulses activate glands and smooth muscles
and
hypothalamus
- secretes releasing hormones to stimulate pituitary gland
CRH - pituitary secretes ACTH - adrenal cortex secretes corticoid hormones
TRH - pituitary secretes TSH - thyroid gland secretes thyroxine
how does the heart adapt to supply more O2 and glucose and remove CO2
- increased heart rate
- increased stroke volume
- increased strength of contractions
what is the cardiovascular centre
a specific part of the medulla oblongata - receives sensory inputs about levels of physical activity, blood CO2 concentration and blood pressure
where are stretch receptors (proprioreceptors) found and what do they detect
in muscles
detect movement in muscles
where are chemoreceptors and what do they detect
carotid artery, aorta, medulla oblongata
detects changes in pH e.g. pH falls as CO2 rises
where are pressure receptors (baroreceptors) found and what do they detect
carotid artery and aorta
detects changes in blood pressure
what is the neurotransmitter for sympathetic NS
noradrenaline
what is the neurotransmitter for the parasympathetic NS
acetylcholine
what are the three types of muscle
- cardiac
- involuntary/ smooth
- voluntary/ skeletal
what is the structure of cardiac muscle
- striated (stripy)
- branched fibres
- powerful contraction
- doesn’t fatigue (no lactic acid)
- respires fatty acids (mainly)
- can’t respire anaerobically (or very little)
what are intercalated discs
cell membranes which fuse to give a gap junction, allow free diffusion of ions
action potentials travel very quickly
- depolarisation - influx of Na+
what is the structure of involuntary/ smooth muscle
autonomic - either para or sympathetic
- not striated/ stripy
- single nucleus
- small bundles of actin and myosin
- contraction is slow
what is a
sarcomere
a functional unit of striated muscle the distance from one adjacent Z line to the next (centre of each light band)
what is the plasma membrane of skeletal muscle fibres called?
sarcolemma
define sarco-
muscle
what are the two types of protein that make up myofibrils
actin - the thinner filament - two strands twisted around
and
myosin - the thicker filament - long rod-shaped fibres with bulbous heads that project to one side
what are the light bands in myofibrils
I (isotopic) bands
actin and myosin don’t overlap
actin not covered by myosin
what are the dark bands in myofibrils
A-bands
darker due to presence of thick myosin filaments
edges darker as as myosin overlapped with actin
just myosin
what is the z-line in myofibrils
found at the centre of each light band (I-band)
distance between adjacent z-lines = sarcomere
where actin filaments meet
what is the H zone in myofibrils
the lighter coloured region found in the centre of each dark band. only myosin filaments present
myosin not covered by actin
what happens to the H-zone and sarcomere when muscles contract
shorten/ decreases as muscle contracts
what should you be able to identify in microscopic sample of skeletal muscle
- individual muscle fibres
- highly structured arrangements of sarcomeres which appear as dark (A) bands and light (I) bands
- streaks of connective and adipose tissue
- capillaries running between the fibres
define the sliding filament model and list the results
during contraction the myosin filaments pull the actin filaments inwards towards the centre of the sarcomere
resulting in:
- light band becoming narrower
- the z-lines moving closer together, shortening the sarcomere
- the H-zone becoming narrower
describe the structure of myosin
- have globular heads that are hinged which allows them to move backwards and forwards.
- on the head is a binding site for each of actin and ATP.
- the tails of several hundred myosin molecules are aligned together to form the myosin filament
describe the
structure of actin
- made of two strands of F actin wrapped around
- each strand contain:
- G actin - globular protein subunits
- tropomyosin - rod shaped protein
- troponin - complex of 3 polypeptides
one binds to G actin
one binds to tropomyosin
one binds to calcium - binding sites for myosin heads
– often blocked by protein tropomyosin
what are the features of voluntary (skeletal) muscle
striated
powerful contraction
fatigues quickly
can respire anaerobically for a short time
what is a neuromuscular junction
the synapse between a muscle and a motor neurone
what is a motor unit
branches of one motor neurone and the muscle cells it stimulates
what is another way the body can generate ATP
using the chemical - creatine phosphate - stored in muscle.
creatine adds the phosphate to ADP to form ATP
what are the pro and con with using creatine phosphate
pro: generates ATP rapidly
con: store of phosphate is used up quickly
when muscles are relaxed, creating phosphate store replenished
how are myofibrils arranged?
one thick filament (myosin) is surrounded by 6 thin filaments (actin)
what is the in depth process of the sliding filament theory of muscle contraction (4 steps)
- myosin head attaches to actin forming a cross-bridge as Pi released
- ADP released - head bends, power stroke, thin filament pulled along
- cross-bridge broken as new ATP attaches to myosin head
4 ATP is hydrolysed to ADP and Pi causing head to move backwards.
what are the 2 essential factors for muscle contraction?
- Ca^2+ available
and ATP available
what is the role of the Ca^2+ in muscle contraction
when muscle is relaxed, tropomyosin and troponin block the binding site for myosin head
when muscle contracts,
Ca^2+ binds to troponin
troponin changes shape
moves tropomyosin away
allows myosin head to bind to actin
