Physiology wk3 Flashcards
1
Q
what are the functions of the nervous system
A
- Control of internal environment – coordinated with the endocrine system, perceives/responds to internal and external environment
- Voluntary control of movement
- Spinal cord reflexes
2
Q
what are the anatomical divisions of the nervous system
A
CNS - brain/spinal
PNS - neurons outsdie the cns
sesnsory division - afferent fibers transmit impulses from receptors to CNS
motor division - efferent fibers transmit impulses from CNS to effector organs
3
Q
what input do we get from the sensory nervous system
A
- Somatic sensory – perceived from receptors (eyes, ears and skin…)
- Visceral sensory – not consciously perceived from receptors of blood vessels/organs (heart)
4
Q
what output is there from the motor nervous system
A
- Somatic motor – conscious/voluntarily controlled (skeletal muscles)
- Autonomic motor – not voluntary (cardiac muscle, smooth muscle and glands)
5
Q
what is an axon
A
it is a nerve fiber, it carries electrical messages as action potentials
6
Q
what is the synapse
A
made up of pre and post, it is the contact point between of one neuron and dendrite of another
7
Q
how can we increase speed of transmission between axons
A
increase axon diameter
increase myelin sheath
increasing temp
8
Q
at rest is membrane potential positive or negative
A
it is negative (-5 to -100 volts)
9
Q
what is resting membrane potential determined by
A
permeability of plasma membrane to ions
difference in ion concentration across the membrane
10
Q
how is negative potential maintained
A
by the sodium potassium pump, 2 k+ go in and 3 Na go out of the cell to remain negative
11
Q
what is an action potential
A
occurs when stimuli of sufficient strength depolarizes the cell
12
Q
how do action potentials increase membrane potential
A
opens Na+ channels and allows them to diffuse into the cell making it more positive
13
Q
what is repolariztion
A
returning the membrane to its resting potential
14
Q
how is repolarization caused
A
k+ leaves the cell rapidly
Na+ channels close
15
Q
what is the all or none law
A
once a nerve impulse is initiated it will travel the length of neuron
has to be large enough
16
Q
how do neurotransmitters work
A
- Chemical messengers released from the presynaptic membrane
- Binds to receptors on postsynaptic membrane
- Causes depolarization of postsynaptic membrane
17
Q
what does EPSP stand for
A
Excitatory postsynaptic potentials
18
Q
what are the two types of neural depolarzation
A
- Temporal summation – rapid and repetitive excitation from a single excitatory presynaptic neuron
- Spatial summation – summing EPSPs from several different presynaptic neurons
19
Q
what does IPSP stand for
A
Inhibitory postsynaptic potentials
20
Q
what do IPSPs do
A
- Causes hyperpolarization (more negatve resting potential)
- Neurons with more negative membrane potential resist depolarization
21
Q
what are joint proprioreceptors made up of
A
- Free nerve endings (touch/pressure)
- Golgi type receptors (found in joint ligaments)
- Pacinian corpuscles (tissues around joints/skin)
22
Q
what are muscle proprioreceptors made up of
A
- Muscle spindles
- Golgi tendon organs
23
Q
what do muscle spindles do
A
respond to change of muscle length and assist the regulation of movement and maintain posture
24
Q
what are muscle spindles made up off
A
- Intrafusal fibers – run parallel to normal muscle fibres(extrafusal fibres)
- Gamma motor neurons – stimulate intrafusal fibres to connect with extrafusal fibres (by alpha motor neuron
25
what is the stretch reflex
stretch on muscle causes reflex contraction (knee-jerk reflex)
26
what does the golgi tendon organ do
* Monitors force development in muscle – prevents muscle damage during excessive force generation
* Stimulation results in reflex relaxation of muscle – inhibitory neurons send inhibitory post synaptic potentials (IPSPs) to muscle alpha motor neuron
ability to oppose gto inhibition will be sue to strength gain
27
where are motor neurons located
within the spinal cord, relay messages to skeletal muscle
28
what is a motor unit
motor neuron and all the muscle fibres it innervates
29
what is the innervation ratio
number of muscle fibres are innervated by a single motor neuron
* Low ratio – fine motor control
* High ratio – not fine muscle control
30
what are the types of motor units
1. Type s (slow/type 1)
2. Type FR (fast, fatigue resistant/type 2a)
3. Type FF (fast fatigable/type 2x)
31
what are the key components of the brain
* Cerebrum/cerebral cortex – organisation of complex movement, storage of learned experiences and reception of sensory information
* Cerebellum – implicated in control of movement and integration of sensory information
* Brainstem – role in cardiorespiratory function, locomotion, muscle tone, receiving information from special senses
32
what makes up the brain stem
* Midbrain – connects the pons and cerebal hemispheres, functions include: controlling responses to sight, eye movement, pupil dilation, body movement and hearing
* Medulla oblongata – involved in control of autonomic function, relaying signals between brain and spincal cord and coordination of body movements
* Pons – involved in sleep and the control of autonomic function, relays sensory information between the cerebrum and cerebellum
33
what is spinal tuning
intrinsic neural networks (central pattern generators) within a spinal cord that refines voluntary movement after getting messages from higher brain centres
34
what is the withdrawl reflex
occurs via reflex arc, where a reflex contraction of skeletal muscles can occur in response to sensory input and is not dependant on activation of higher brain centres
35
control of voluntary movement needs co-ordination of what subcortical areas
1. Motor cortex receives input from variety of brain areas (basal nuclei, cerebellum, thalamus)
2. Spinal mechanism (spinal tuning) results in refinement of motor control
3. Feedback from proprioceptors allows for further modification
36
what does the parasympathetic system control
resting and digestion
37
what does sympathetic system control
fight or flight, regulates blood flow and increases cardiac output
38
what comes under autonomic processes
Hr and blood pressure
39
where in the spinal cord does the sympathetic nervous system travel from
T1-L2 (thoratic and lumbar region)
40
where in the CNS does the parasympathetic nervous system travel from
within the brain stem and sacral region
41
what does cholinergic mean
any fiber that secretes acetylcholine
42
what does adrenergic mean
any fiber that secretes epinephrine/NE
adrenalin
43
what is different about para/sympathetic nervous system cell bodies hormone release
para shoots ach from pre and post ganglionic neurons
symp shoots ach from pre ganglionic but also fires NE and ACH from post ganglionic neurons
44
what is the difference in size of the pre and post ganglionic neurons in the two different systems
in para there is longer axons and synapses are closer to the effectors,
in symp there is shorter axons further away from the effectors
45
how does the para system work to reduce HR
neurons from the CCC (vagus nerve) release ACH that links to the SA and AV node , this decreases their activity
46
how does the symp system work
neurons from the spinal cord act as cardiac accelerators, release NE onto beta receptors on the heart to increase HR
47
what causes initial raise in HR
parasypathetic withdrawl and SNS outflow
48
how is stroke volume regulated
1. End-diastolic volume – volume of blood pumped in the ventricles at the end of diastole (preload)
2. Average aortic blood pressure – pressure the heart must pump against to eject blood, mean arterial pressure (afterload)
3. Strength of the ventricular contraction (contractility) – enhanced by circulating epinephrine and norepinephrine and direct sympathetic stimulation of heart
49
what does increase in afterload cause
lower SV during resting conditions
50
what is frank starlings law
increase in venous return leading to improved SV
51
how is venous return increased
* Venoconstriction – via SNS
* Skeletal muscle pump – contraction squeezes veins forcing blood movement
* Respiratory pump – changes in thoracic pressure pulls blood towards the heart
52
what is systolic presssure
pressure generated during ventricular contraction
53
what is diastolic pressure
pressure in arteries in cardiac relaxation
54
what is pulse pressure
difference between systolic and diastolic pressure
55
what is mean arterial pressure
average pressure in the arteries map = dab + 0.33 (sbp – dbp)
56
formula for MAP
cardiac output x total vascular resistance (sum of resistance to blood flow)
57
what are the short term regulators for blood pressure
* Sympathetic nervous system
* Baroreceptors in aorta and carotid arteries – increase in BP = less SNS activity, decrease in BP = increased SNS activity
58
where in the body controls long term regulation of blood volume
the kidney
59
how is increased blood flow to skeletal muscles done
1. Increased cardiac output
2. A redistribution of blood flow from inactive organs to the working skeletal muscles
60
what do changes in hr and bp depend on
* Type, intensity and duration of exercise
* Environmental conditions
* Emotional influence before and during exercise – due to increases in SNS activity
61
how does the body transition from rest to exercise
Onset – rapid increase in HR, SV and Q. plateau in submaximal exercise
Recovery – decreased HR, SV and Q. depends on intensity and training type
62
what does recovery of hr and bp between bouts depend upon
* Fitness level
* Temp and humidity
* Duration of intensity of exercise
63
what is the cv drift
Gradual increase in hr when prolonged exercise due to decreased SV
64
what are the measures of energy expenditure
* Direct calorimetry – measures heat exchange between human body and the environment
* Indirect calorimetry – measures type and rate of substrate utilization, estimated from gas exchange
* Doubly labelled water – measures total carbon dioxide production by observing the different rates of elimination of a bolus dose of the stable isotope tracers (hydrogen and oxygen)
65
what does the ANS do
maintains homeostasis at rest and in response to changes in physiological state, these changes in homeostasis are achieved through parasympathetic and sympathetic nervous systems.
66
what are the accurate measurements of HR/HRV
* Electrocardiogram (ECG) – criterion measure
During each heartbeat, the heart depolarizes and repolarizes resulting in electrical charges on the skin.
* Photoplethysmography (PPG) – reliable and valid
Properties in skin and tissue are always changing due to blood-flow, by using light emitters towards the skin the photosensor can measure light absorption
67
what is heart rate variability
Premise – beat-to-beat variation in the length of cardiac cycles
Interpretation – the greater the HRV, the greater the modulatory influence of the cardiac vagus on heart rate
timing between heart beats
greater hrv = healthier
68
what are the acute stressors
* Hard workout
* Intercontinental travel
* Drinking alc
* Caffeine
69
what are the chronic stressors
* Work/study
* Infection
* Illness
70
what does sensitivity mean
capacity of an organism or sense organ to respond to stimulation
71
what does reactivity mean
the quality or state of being reactive or readily responsive to a stimulus, due to stress
