communication, homeostasis and energy Flashcards
(175 cards)
1
Q
what is the central nervous system composed of?
A
brain
spinal cord
2
Q
what does the central nervous system contain?
A
relay neurons
3
Q
what is the peripheral nervous system composed of?
A
cranial nerves
spinal nerves
peripheral nerves
4
Q
what does the peripheral nervous system contain?
A
sensory neurons
motor neurons
5
Q
where is the cell body located in a motor neuron?
A
on the end of the axon
on the left side
6
Q
what is the cell body of a neuron called?
A
soma
7
Q
what is the sequence of the nervous system?
A
- stimulus
- receptor cells
- sensory neurons
- CNS (relay neurons)
- motor neuron
- effector
- response
8
Q
what is the peripheral nervous system divided into?
A
sensory division
motor division
9
Q
what is the sensory division made up of?
A
sensory neurons
10
Q
what does the sensory division do?
A
signals from receptors to CNS
11
Q
what is the motor division made up of?
A
motor neurons
12
Q
what does the motor division do?
A
signals from CNS to receptors
13
Q
what is the motor division divided into?
A
autonomic nervous system
somatic nervous sytem
14
Q
what does the autonomic nervous system do?
A
controls involuntary responses
15
Q
what does the somatic nervous system do?
A
controls voluntary movement
16
Q
what is the autonomic nervous system divided into?
A
sympathetic division
parasympathetic division
17
Q
what does the sympathetic division do?
A
mobilises body systems
‘fight or flight’ responses
18
Q
what does the parasympathetic division do?
A
conserves energy
‘rest and digest’ responses
19
Q
what is the stimulus pathway?
A
- stimulus
- receptor
- sensory neuron
20
Q
what are the types of stimulus?
A
physical (temp/press/light)
chemical
21
Q
what is a biological transducer?
A
receptors
converts stimuli into electrical signals
22
Q
what is mechanical pressure?
A
pressure caused by a physical force
23
Q
what is the pacinian corpuscle?
A
receptor that responds to mechanical pressure
transduce mechanical energy of the stimulus into a generator potential
24
Q
what are photoreceptors?
A
respond to light
found in the eye
25
what are chemoreceptors?
respond to chemicals
found in the nose
26
what are mechanoreceptors?
respond to mechanical strain/stretching
found in the skin
27
what are baroreceptors?
respond to blood pressure
found in blood vessels and the heart
28
what are osmoreceptors?
respond to bodily fluids
found in the hypothalamus and cartoid artery
29
what is action potential?
a nerve impulse which causes depolarisation of the nerve cells membrane by ions moving across
30
what are the 3 main stages in creating action potential?
depolarisation
repolarization
refractory period
31
what gets pumped out in the sodium-potassium pump?
3 sodium ions (NA+)
32
what gets pumped in the sodium-potassium pump?
2 potassium ions (K+)
33
what are mylinated nerve fibres?
made of schwann cells which wrap around the axon
have high lipid content to create insulated layer
34
what helps cause faster nerve impulses?
wider diameter of neurons
myleniated diameters
35
what is multiple sclerosis?
autoimmune condition
affects around 100,000 people in the UK
mistakenly attacks the myelin sheath in the brain and spinal cord
unknown triggers (genetic + environmental factors)
36
how does multiple sclerosis slow down nerve impulses?
due to breaking down the mylin
can affect axons so interrupts signals passing
37
where is the pacinian corpuscle found?
deep within the skin
in the dermis layer
(in skin of fingers, soles of feet, tendons + ligaments)
38
whats the structure of the pancinian corpuscle?
made of many layers of membrane around the end of the neurone seperated by a gel
contains a blood capillary, capsule and sensory neuron
39
what does the gel between the layers in a pacinian corpuscle contain?
positively charged sodium ions (NA+)
40
how is action potential formed in sensory neuron?
1. normal resting state - too narrow to allow sodium to move through
2. pressure applied - change shape so neuron membrane stretch
3. membrane stretches - sodium channels widen, NA+ diffuses in
4. depolarises membrane - results in generator potential
5. action potential is generated
41
what is depolarisation?
an electrical change within a neuron from a (relatively) negative charge to a positive charge
42
what happens in depolarisation?
Na channels open
influx of sodium in
membrane to become more positive
43
what is repolarisation?
an electrical change within a neuron from a (relatively) positive charge to a negative charge
44
what happens in repolarisation?
(after an influx of Na+) potassium channels open
as K+ is more concentrated inside the neuron, it moves out
causes the inside to become relatively negative again
45
what is the refractory period?
period in which neuron is unresponsive to stimulation (ion distribution is being restored)
46
what happens in the refractory period?
the membrane is hyperpolarised
voltage dependent potassium channels now close
K+ diffuses back into the axon
sodium-potassium pump restores the resting potential
47
what is the course of events (+what happens) in nerve impulses?
1. resting potential (Na+/K+ pump)
2. depolarisation (voltage gated Na+ channel opens)
3. repolarisation (voltage gated K+ channel opens)
4. resting potential (Na+/K+ pump)
48
what is saltatory conduction?
increases nerve transmission
Na+ inflow at node generates action potential
gives impression that influxes jump to node of Ranveirs
49
whats a synaptic cleft?
tiny gap between cells at the synapse
50
what does the synaptic knob contain?
synaptic vesicles filled with neurotransmitters
51
how does the response not keep happening after action potential occurs?
removed from the cleft
taken back into the presynaptic neurone
broken down by enzymes
52
how do neurotransmitters transmit nerve impulses between neurones?
1. an action potential triggers calcium influx
2. calcium influx causes neurotransmitter release
3. the neurotransmitter triggers an action potential in the postsynaptic neurone
53
what is an excitatory synapse?
neurotransmitters depolarise the postsynaptic membrane and make it fire an action potential if the threshold is reached
54
what is an inhibitory synapse?
when neurotransmitters bind to receptors on postsynaptic membrane they hyperpolarise the membrane (more negative) which prevents an action potential from being fired
55
what is synaptic divergence?
when one neuron connects to many neurons information can be dispersed to different parts of the body
56
what is synaptic convergence?
when many neurons connect to one neurone information can be amplified
57
what is spatial summation?
signals from multiple stimuli are coordinated into a signal response
small amount of neurotransmitter released from each neuron can be enough altogether to reach the threshold
58
what is temporal summation?
where two (or more) nerve impulses arrive in quick succession from the same presynaptic neuron
makes an action potential more likely since more neurotransmitter is released into the synaptic cleft
59
how can glands be stimulated?
by a change in concentration of a specific substance (sometimes another hormone)
by electrical impulses
60
how do hormones travel?
in the bloodstream
in the circulatory system
61
what is a target cell?
where there is specific receptors found on the membranes
62
what's the order of the hormonal system sending chemicals?
1. stimulus
2. receptors
3. hormone
4. effectors
5. response
63
why is a hormone a first messenger?
it carries the chemical message the first part of the way
(from endocrine gland to receptor on the target cells)
64
what happens when a hormone binds to its receptor?
it activates an enzyme in the cell membrane
65
what happens once the enzyme is activated in the cell membrane?
it catalyzes the production of a signaling molecule
66
what is a signalling molecule?
it signals to other parts of the cell to change how the cell works
67
why is a signalling molecule a second messenger?
it carries the chemical message the second part of the way
(from receptor to other parts of the cell)
68
what do second messengers do?
activate a cascade inside the cell
69
example: adrenaline
(trigger second messenger pathway)
1. adrenaline as first messenger
2. binds to specific receptors in the cell membranes
3. activates the enzyme adenylyl cyclase
4. catalyses production of second messenger cyclic AMP (cAMP) from ATP
5. cAMP activates a cascade to make more glucose available
70
what are the parts of the adrenal glands?
outer part = cortex
inner part = medulla
71
what does the cortex secrete?
steriod hormones
(eg cortisol and aldosterone when stressed)
72
what does cortisol and aldosterone do?
role in short term and long term response to stress
- stimulate breakdown of proteins and fats into glucose
(increases energy)
- increasing blood volume and pressure
(by increasing uptake of sodium ions and water by the)
- suppressing the immune system
73
what does the medulla secrete?
catecholamine hormones (modified amino acids)
(eg adrenaline and noradrenaline when stressed)
74
what does adrenaline and noradrenaline do?
make more energy available in short term by:
- increasing heart rate and breathing rate
- causing cells to break down glycogen into glucose
- constricting some blood vessels so blood gets diverted to the brain and muscles
75
what are islets of Langerhans?
contain endocrine tissue
found in clusters around blood capillaries
secrete hormone directly into the blood
76
what are the types of endocrine tissues?
alpha cells and beta cells
77
what does alpha cells do?
secrete glucagon
77
what does beta cells do?
secrete insulin
78
what is an ectotherm?
can't control their body temperature internally
control by changing their behaviour
internal temperature depends on the external temperature
have variable metabolic rate
79
what is an endotherm?
control their body temperature internally by homeostasis
constantly high metabolic rate and generate a lot of heat from metabolic reactions
80
what body mechanisms reduce body temperature?
sweating
hairs lie flat
vasodilation
81
how does sweating reduce body temperature?
sweat glands secrete more sweat when the body's too hot
water in sweat evaporates from surface of skin
this takes heat from the body and so cools skin
82
how does hair lying flat reduce body temperature?
when its hot, erector pili muscles relax so the hairs lie flat
less air gets trapped so skin is less insulated and heat gets lost more easily
83
how does vasodilation reduce body temperature?
aterioles near the surface of the skin dilate
more blood flows through the capillaries in the surface layer of the dermis
so more heat is lost from the skin by radiation so temperature lowers
84
what body mechanisms increase body temperature?
shivering
much less sweat
hairs stand up
vasoconstriction
hormones
85
how does shivering increase body temperature?
muscles contract in spasms to cause shivering
more heat is produced from increased respiration
86
how does hairs standing up increase body temperature?
erector pili muscles contract to make the hairs stand up
this traps more air and so prevents heat loss
87
how does vasoconstriction increase body temperature?
when its cold, arterioles near the skin constrict
so less blood flows through the capillaries in the surface layers of the dermis
this reduces heat loss
88
how does hormones increase body temperature?
adrenaline and thyroxine are released
this increases metabolism so more heat is produced
89
how does the hypothalamus control body temperature in mammals?
1. hypothalamus recieves information from thermoreceptors via senseory neurones
2. it then send impulses along motor neurones to effectors
3. effectors restore body temperature
90
where are thermoreceptors found?
- hypothalamus (detect internal temperature)
- skin (peripheral temperature receptors) (detect external temperature)
91
what is the normal body temperature?
37 degrees
92
what is the normal blood glucose concentration?
90 mg (per 100cm3 of blood)
93
how does blood glucose naturally rise?
after eating food containing carbohydrates
94
how does blood glucose naturally fall?
after exercise
95
how does insulin lower blood glucose?
1. insulin binds to specific receptors (on membranes of liver and muscle cells)
2. increases permeability of cell membranes to glucose - so cells take up more glucose
3. insulin also activates enzymes that convert glucose to glycogen
4. cells store glycogen in their cytoplasm
5. also increases rate of respiration
96
how does glucagon raise blood glucose?
1. glucagon binds to specific receptors (on membranes of liver cells)
2. also activates enzymes that break down glycogen into glucose
3. glucagon also promotes formation of glucose from glycerol and amino acids
4. also decreases the rate of respiration
97
what is the process of forming glycogen from glucose?
glycogenesis
98
whats the process of breaking down glycogen?
glycogenolysis
99
whats the process of forming glucose from non-carbs?
gluconeogenesis
100
what happens when blood glucose is too low? (negative feedback)
1. pancreas detects blood glucose is too low
2. alpha cells secrete glucagon + beta cells stop secreting insulin
3. glucagon binds to liver cell receptors
4. glycogenolysis is activated + gluconeogenesis is activated + cells respire less glucose
5. cells release glucose into the blood
normal blood glucose concentration is restored
101
what happens when blood glucose is too high? (negative feedback)
1. pancreas detects blood glucose is too high
2. beta cells secrete insulin + alpha cells stop secreting glucagon
3. insulin binds to receptors on liver and muscle cells
4. cells take up more glucose + glycogenesis is activated + cells respire more glucose
5. less glucose in the blood
normal blood glucose concentration is restored
102
how does beta cells secrete insulin?
1. when BGC is high more glucose enters beta cells by facilitated diffusion
2. causes rate of respiration to increase, making more ATP
3. this triggers the potassium ion channels in b cells to close
4. potassium ions build up inside the cell
5. inside b cell is less negative so the plasma membrane is depolarised
6. this causes calcium ion channels to open so calcium ions diffuse in
7. causes vesicles (containing insulin) to fuse with b cell plasma membrane and releasing insulin (by exocytosis)
103
what is type 1 diabetes?
autoimmune disease where T killer cells destroys b cells in islets of Langerhans
so don't produce any insulin
104
how to treat type 1 diabetes?
- regular insulin injections
- islet cell transplant
- diet + exercise
105
what is type 2 diabetes?
when b cells don't produce enough insulin or body cells don't respond properly to insulin
insulin receptors on the membranes don't work properly
106
how to treat type 2 diabetes?
- lifestyle changes (diet + exercise)
medication
- metformin (reduce amount of glucose liver cells release)
- sulfonylureas (pancreas to produce more insulin)
- thiazolidenediones (make body cells more sensitive to insulin)
107
how can human insulin be made?
by genetically modified (GM) bacteria
108
what are benefits of using GM insulin?
- cheaper
- large quantities can be made
- less likely to get rejected
- less ethical issues
109
how can stem cells be used to cure type 1 diabetes?
stem cells grow into b cells which get implanted into the pancreas
110
what are the main functions of the kidney?
- excrete waste products
- regulate water potential of the blood
111
how does kidneys excrete waste products?
1. blood enters kidney through renal artery then passes through capillaries in the cortex of the kidneys
2. substances get filtered out of blood into long tubules that surround capillary (ultrafiltration)
3. useful substances are reabsorbed back into blood from tubules in the medulla and cortex (selective reabsorption)
4. remaining unwanted substances pass along tubules, then along ureter to the bladder (where expels as urine)
5. filtered blood passes out of kidneys through renal vein
112
what is a nephron?
long tubules along with the bundle of capillaries
where blood is filtered
around 1 milion in each kidney
113
what is process of blood filtering in the nephron?
1. blood from renal artery enters smaller arterioles in the cortex
2. each arteriole splits into a glomerulus (bundle of capillaries looped inside hollow ball known as Bowman's capsule)
3. ultrafiltration occurs
4. high pressure forces liquid and small molecules out of capillary and into bowman's capsule (passing though three layers) and enter the nephron tubule
5. larger molecules can't pass through and stay in the blood
6. liquid and small molecules filtrate and pass along the nephron where useful substances get reabsorbed
7. filtrate flows through the collecting duct and passes out of kidney along the ureter
114
what is the afferent arteriole?
takes blood IN to each glomerulus
115
what is the efferent arteriole?
takes filtered blood AWAY from the glomerulus
smaller in diameter so creates high pressure
116
what are the three layers to get into the bowman's capsule?
- the capillary wall
- the basement membrane
- the epithelium of the Bowman's capsule
117
what does the hypothalamus control?
body temperature
118
what does the pituitary gland control?
hormone release by body glands
119
what does the medulla oblongata control?
breathing rate and heart rate
120
what does the cerebrum do?
allows you to see, hear, learn + think
121
what does the cerebellum do?
coordinates muscles, balance and posture
122
how does the blinking reflex occur?
1. sensory nerve endings in the cornea are stimulated by touch
2. a nerve impulse is sent along the sensory neurone to a relay neurone in the CNS
3. the impulse is then to a motor neurone
4. then arrives at effectors
123
what are the effectors in the blinking reflex?
orbicularis oculi muscles (that move your eyelids)
124
how does the knee jerk reflex occur?
1. stretch receptors in the quadriceps muscle detect that the muscle is being stretched
2. a nerve impulse is passed along a sensory neuron which goes directly to a motor neuron in the spinal cord
3. the motor neuron carries the nerve impulse to the effector
4. the quad muscle contracts so the lower leg moves forward quickly
125
what is skeletal muscles made up of?
muscle fibres (large bundles of long cells)
126
what is the cell membrane of muscle fibre cells called?
sarcolemma
127
what is the structure of a muscle fibre?
- bits of the sarcolemma fold inwards across the muscle fibre and stick to the sarcoplasm
- a network of internal membranes (sarcoplasmic reticulum) run through the sarcoplasm
- have lots of mitochondria
- multinucleated
- have lots of long, cylindrical organelles (myofibrils)
128
what are transverse T tubules?
bits of sarcolemma folded inwards in muscle fibres
they help to spread electrical impulses to reach all parts of the muscle fibre
129
what does the sarcoplasmic reticulum store?
calcium ions
130
what do myofibrils contain?
thick myofilaments
thin myofilaments
131
what are thick myofilaments made from?
myosin (a protein)
132
what are thin myofilaments made from?
acton (a protein)
133
what are dark bands in myofibrils?
contain thick myosin filament and some overlapping thin actin filaments
called A bands
134
what are light bands in myofibrils?
contain thin actin filaments only
called I bands
135
what are myofibrils made up of?
sarcomeres
136
what lines mark the sarcomeres?
ends = z line
middle = m line
137
what is the h zone?
around the m line
only contains myosin filaments
138
what is the sliding filament theory?
1. myosin and actin filaments slide over one another to make the sarcomeres contract
2. the simultaneous contraction of lots of sarcomeres means the myofibrils and muscle fibres contract
3. sarcomeres return to their original length as the muscle relaxes
139
what is a myosin head?
- a globular head to myosin filments that are hinged
- each has a binding site for actin and for ATP
140
what is found between actin filaments?
tropomyosin and troponin (proteins)
these are attached to each other
141
what happens in resting muscles?
the actin-myosin binding site is blocked by tropomyosin (which is held in place by troponin
so myofilaments can't slide past each other since the myosin heads can't bind to the binding site on the actin filaments
142
how is muscle contraction triggered by an action potential?
1. action potentila triggers an influx of calcium ions
2. ATP provides the energy needed to move the myosin head and break the cross bridge
143
how does the action potential trigger an influx of calcium ions in muscle contraction?
1. the action potentila from a motor neurone stimulates a muscle cell and depolarises the sarcolemma
2. depolarisation spreads down the T-tubules to the sarcoplasmic reticulum
3. calcium ions bind to troponin (causing it to change shape) so pulls the attached tropomyosin out of the binding site
4. allows the myosin head to bind since it exposes the binding site
5. this forms an actin-myosin cross bridge
144
how does ATP provide the energy needed to move the myosin head in muscle contraction?
1. calcium ions activate the enzyme ATPase (breaks down ATP into ADP + P) to provide energy needed
2. energy released moves the myosin head which pulls the actin filament along
145
how does breaking the cross bridge help muscle contraction?
1. the myosin head detaches from the actin filament after it's moved
2. myosin head then reattches to a different binding site further along and a new cross bridge is formed
3. many cross bridges form and break rapidly - pulling the actinb filament along (shortens the sarcomere and causes the muscle to contract)
146
what happens when excitation stops in muscle contraction?
1. calcium ions leave their binding sites on the troponin molecules and are moved back into the sarcoplasmic reticulum by active transport
2. troponin molecules return to their original shape and pull the attached tropomyosin molecules back with them
3. actin-myosin binding sites are blocked again
4. actin filaments slide back to thier relaxed position and so lengthens the sarcomere
147
how is energy provided for muscle contraction?
- areobic respiration
- anearobic respiratin
- ATP-creatine phosphate system
148
how is most ATP generated?
via oxidative phosphorylation in the cell's mitochondria
149
how does anaerobic respiration provide energy for muscle contraction?
- ATP is made rapidly by glycolysis
- end product is pyruvate (converted to lactate by lactate fermentation)
- lactate can quickly build up in the muscles and cause muscle fatigue
150
how does the ATP-creatine phosphate (CP) system provide the energy for muscle contraction?
- ATP is made by phosphorylating ADP (adding a phosphate group taken from creatine phosphate)
- CP is stored inside cells and so generates ATP very quickly
151
what is a neuromuscular junction?
synapses between a motor neuron and a muscle cell
152
how do neuromuscular junctions work?
use the neurotransmitter acetylcholine which binds to nicotinic cholinergic receptors
acetylcholinesterase (AChE) is stored in clefts on the postsynaptic membrane and is released to break down acetylcholibe after use
153
what are the three types of muscle?
- skeletal muscle (voluntary muscle)
- involuntary muscle (smooth muscle)
- cardiac muscle
154
what are the properties of skeletal muscle?
- contraction is controlled consciously
- made from many muscle fibres
- contain short twitch and long twitch fibres
- striated
- multi-nucleated
155
what are the properties of involuntary muscle?
- contraction controlled unconciously
- non striated
- found in the walls of hollow internal organs
- uni-nucleated
- contract slowly and don't fatigue
156
what are properties of cardiac muscle?
- contracts on its own (myogenic)
- found in walls of heart
- made of muscle fibres connected by intercalated discs (low electrical resistance)
- branched muscle fibres
- uni-nucleated
- striated
- contract rhythmically and don't fatigue
157
what are the stages of aerobic respiration?
1. glycolysis
2. link reaction
3. krebs cycle
4. oxidative phosphorylation
158
where does glycolysis take place?
in the cytoplasm
159
where does link reaction take place?
in the matrix of the mitochondria
160
where does krebs cycle take place?
in the matrix of the mitochondria
161
where does oxidative phosphorylation take place?
in the inner membrane of the cristae of the mitochondria
162
what are the 3 stages of glycolysis?
1. phosphorylation
2. hexosplitting
3. oxidation of GP
163
what happens in phosphorylation in glycolysis?
energy investment
glucose becomes hexose 1,6 biphosphate
(at the same time) 2ATP = 2ADP + Pi
164
what is hexose 1,6 biphosphate?
more reactive
unable to leave the cell
165
what happens in hexosplitting in glycolysis?
hexose 1,6 biphosphate (6C) becomes 2 x glycerate 3 phosphate (GP) (3C)
166
what happens in oxidation of GP?
- energy payback
glycerate 3 phosphate becomes pyruvate
(at the same time): 2ADP + Pi = 2ATP and NAD+ = NADH + H+
167
what is the end product of glycolysis in respiration?
2 molecules of pyruvate
168
what is the products per glucose molecule in the link reaction? (respiration)
- 2 x CO2
- 2 x NADH
- 2 x acetyl CoA
169
how does pyruvate enter the mitochondrion?
through a transport protein by active transport
170
what happens when pyruvate produces CO2 in the link reaction?
decarboxylated by a decarboxylase enzyme
171
what happens when NAD becomes NADH + H+ in the link reaction?
deohydrogenated by a dehydrogenase enzyme
172
what does pyruvate produce in the link reaction?
acectate (2C)
173
what happens at the same time as pryuvate produces acectate in the link reaction?
CO2 is produced
NAD+ becomes NADH + H+
174
