Communication and Homeostasis Flashcards
1
Q
Name the neurone structures
A
Cell body, Dendrons, Axon, Schwann cells, Myelin sheath, Nodes of Rnaveir
2
Q
What are dendrons
A
Carry nerve impulses towards the cell body
3
Q
What is an axons
A
Single long fibre that carries nerve impulses away from the cell body
4
Q
What are Schwann cells
A
Cells that surround axon by wrapping around many times, protecting it and providing electrical insulation
5
Q
What is a myelin sheath
A
Forms covering of axon and made of membranes of Schwann cells, rich in myelin
6
Q
What are nodes of ranveir
A
Gaps between adjacent Schwann cells where there is no myelin sheath
Gaps are 2-3um and occur every 1-3mm
7
Q
What is a Pacinian corpuscle
A
Rings of connective tissue wrapped around the end of a sensory neurone
Pressure against the skin deforms the connective tissue and pushes it against the nerve ending
8
Q
What is a reflex action
A
An automatic, involuntary and rapid response to a stimulus
9
Q
What is the purpose of a nerve cell body
A
They are involved in the production of neurotransmitters and proteins
10
Q
What are the roles of the synapses in the nervous system
A
Ensure impulses are unidirectional
Allow an impulse from 1 neurone to reach multiple other neurones - creating a number of simultaneous responses
Allows impulses from different neurones to feed into the same synapse - resulting in one response
10
Q
Why does Ach need to be recycled
A
To avoid Na+ continuously diffusing into the postsynaptic membrane and causing multiple action potentials to fire off
10
Q
What is a cholinergic synapse
A
A synapse that uses the neurotransmitter acetylcholine (Ach)
11
Q
What is the resting potential
A
-70mV
12
Q
What is the threshold potential
A
-50 mV
13
Q
What is the action potential peak
A
+40 mV
14
Q
What are endocrine glands
A
Groups of cells specialised to secrete hormones directly into the bloodstream
15
Q
What hormone do alpha cells secrete
A
Glucagon
16
Q
What hormone do Beta cells secrete
A
insulin
17
Q
What are the features of a good communication systen
A
Spans whole body
Cell communication
Specific
Rapid
Short and long term
18
Q
What is the neuronal signalling system
A
A network of interconnecting neurones that produce rapid responses to changing stimuli
19
Q
What is a hormonal signalling system
A
Uses the blood to transport hormones from endocrine glands to target organs. Can be used to produce longer term responses
20
Q
What is homeostasis
A
The act of maintaining a constant internal environment despite external changes
21
Q
What are endo and ectotherms
A
Endotherms - warm blooded
Ectotherms - cold blooded
22
Q
What are the advantages and disadvantages of ectotherms
A
+ Uses less food in respiration
+ Greater proportion of energy used for growth
- less active in cooler temps
- may not be capable of activity in winter months
23
What are the advantages of Endotherms
+ Constant, optimal body temp
+ Activity possible even when cool
+ Can inhabit colder parts of the planet
- Energy used up to maintain constant temp
- More food required
- Less energy used in growth
24
How do endotherms monitor the temperature of their blood
Peripheral temperature receptors in the skin monitor the temperature in the extremities and feed information to the thermoregulatory centre in hypothalamus
Acts as an early warning system
25
What is vasodilation and vasoconstriction
Stimulated by nervous signals from hypothalamus; smooth muscle in the arterioles and pre-capillary sphincter muscles at skin surface relax or contract to dilate or constrict
Inc vessel diameter = inc blood flow to skin = inc amount of heat lost by radiation to air
26
How does sweating work
Stimulated directly by motor neurones from hypothalamus
Water in sweat evaporated from skin surface. The high latent heat of vaporisation causes heat energy to be lost
27
How do hair and fathers regulate temp
Too cold: erector muscles contract to raise hair/feathers trapping air to use as an insulator
Too hot: erector muscles relax, feathers/hair lie flat. insulation reduced so more heat loss by radiation
28
What does the hypothalamus stimulate when temp is too low
Stimulates thyroid and adrenal glands to releases thyroxine and adrenaline to increase metabolic activity - leading to more exogenic reactions and more heat being releases
Involuntary muscle spasm (shivering) causes more respiration - more heat release
29
What are sensory receptors
A specialised cell or sensory neurone ending that can detect changes in the environment and may generate a nerve impulse as a result of a stimulus
They are tranducers
30
What are tranducers
Convert energy in one form to electrical energy in the form of a nerve impulse
31
How does a Na+/K+ pump work
3 Na+ are actively transported out, 2 K+ are transported in - this creates a charge imbalance
32
How is an action potential generated
A stimulus is detected, causing some Na+ channels to open. Charge increases from -70 to a threshold potential (-50mV) causing all voltage gated Na+ channels to open - this is known as depolarisation
At the AP peak, Na+ gates close and K+ gates open - repolarisation
Then it undergoes a refractory period in which K+ gates close - hyperpolarisation
Na+/K+ pumps restore resting potential
33
Why is there a refractory period
To ensure each AP is unique
34
What is the transmission of an action potential in an unmyelinated neurone
Na+ diffuses into neurone through a channel
There is a localised high concentration of Na+ inside the neurone
Na+ diffuses along the inside of the neurone
Na+ gate opens due to depolarisation
There is a series of local circuits
35
How does transmission of AP happen in a myelinated neurone
Ionic exchanges occur only at Nodes of Ranvier. Na+/K= cant diffuse through myelin
There are elongated local currents
Action potential jumps from one node to the next in a process called saltatory conduction
36
What are the advantages of having a myelin sheath
Insulates
Speeds up transmission
Fewer channels needed
37
What effects the speed of an impulse
Axon diameter - inc diameter = inc speed
Temperature - inc temp = int diffusion = inc speed
Too high a temp = denaturing of channels
38
What are the parts of a synapse
Axon, synaptic vesicles, synaptic cleft, neurotransmitter, receptor, dendrites
39
What is a synapse
Where two neurones meet but dont touch
40
What happens when an AP reaches a cholinergic synapse
AP arrives at presynaptic bulb
Voltage gated Ca2+ channels in presynaptic bulb open - Ca2+ diffuses in
Synaptic vesicles containing acetylcholine move to and diffuse with presynaptic membrane
Ach is released by exocytosis and diffuses across synaptic cleft
Ach binds to receptor site on Na+ channel receptors on postsynaptic membrane
Na+ channels open - Na+ diffuses into postsynaptic neurone
Generator potential produced - if it reaches threshold potential an AP will fire
41
How is the recycling of acetylcholine done
Ach is broken down by hydrolytic enzyme acetylcholinesterase
Ach is hydrolysed into ethanoic acid and choline - both diffuse back across synaptic cleft and re-enter presynaptic bulb
ATP from mitochondria is used to reform Ach
42
Why is ach recyckes
To stop sodium ions from continuously diffusing into postsynaptic membrane - stops multiple APs from firing
43
What are the features of synapse
Spatial summation
Temporal summation
1 pre converges into many post
many pre converge into one post
Unidirectional
Filters out low level stimuli
Acclimatisation
Summations
inhibition
44
What is spatial summation
Many presynaptic neurones share 1 synaptic cleft + postsynaptic neurone
together they release enough neurotransmitters to create AP
45
What is temporal summation
1 presynaptic neurone releases neurotransmitters many times over a short period
AP is sent if neurotransmitter exceeds threshold value
46
How are synapses involved in inhibition
Cl- channels in postsynaptic membrane
If these open, Cl- flows into postsynaptic neurone - causing hyperpolarisation
Harder to achieve an action potential
47
What are exocrine glands?
Glands that secrete chemicals through ducts onto a surface
48
What are hormones
Messenger molecules released by endocrine glands into the blood
Act as signals for target tissues/organs
49
What are some examples of non-steroid hormones
Adrenaline
Insulin
Glucagon
ADH
50
What are some examples of steroid hormones
Oestrogen
Testosterone
51
What is the difference between steroid and non-steroid hormones
Steroid - enter the cell and have a direct effect on the DNA in the nucleus
Non-steroid - dont enter the cell, bind to receptors in the cell surface membranes
52
What is the mechanism of non-steroid hormones
hormone = first messenger. As it is hydrophilic it cannot pass through the cell membrane and instead binds to specific receptors on cell surface of target cells
When a hormone binds to a complimentary receptors, a G protein is activated
This activates an enzyme called adenyl cyclase which converts ATP to cAMP
cAMP = second messenger, can act directly on another protein, stimulate transcription or initiate a cascade of enzyme controlled reactions
53
What is the mechanism for steroid hormones
Pass through plasma membrane, bind to steroid hormone receptors in cytoplasm or nucleus - forms a hormone-receptor complex
Complex acts as a transcription factor and can facilitate or inhibit the transcription of a specific gene
54
What hormones are produced by adrenal cortex and its function
Aldosterone - steroid hormone that controls Na+ and K+ concentrations in blood
Cortisol - steroid hormone that controls metabolism of carbohydrates + proteins in liver
55
What does the adrenal cortex use to produce steroid hormones
Cholesterol
56
Where are the adrenal cortex hormones produced
Alsosterone - zona glomerulosa
Cortisol - zona fasciculata
sex hormones - zona reticularis
57
What hormone is produced in the Adrenal Medulla
Adrenaline and noradrenaline
58
What is the role of adrenaline
A peptide hormone that is secreted in response to stress
Relaxes smooth muscle in bronchioles
Increases stroke volume of the heart
Increases heart rate
59
What is the exocrine function and mechanism in the pancreas
Secretes enzymes
Pancreatic cells surround tubules which drain into the pancreatic duct (acini)
Pancreatic cells produce pancreatic juice made up of Amylase, trypsinogen, lipase
60
What is the endocrine function of the pancreas
Hormones are secreted from the cells in the islets of Langerhans
61
What is an acini
Any cluster of cells that resemble a many lobed berry
62
What happens when a raised glucose level is detected
Change is detected in beta cells of the islets of Langerhans, beta cells secrete insulin into blood, insulin is detected by receptors on liver and muscle cells
Liver and muscle cells remove glucose from the blood and convert glucose to glycogen (glycogenesis)
63
What is glycogenesis, glycogenolysis, gluconeogenesis
glycogenesis = glucose -> glycogen
glycogenolysis = glycogen -> glucose
gluconeogenesis = new glucose made
64
What happens when blood glucose conc falls
Detected by alpha cells in islets of Langerhans
Alpha cells secrete glucagon into blood
Glucagon detected by receptors on liver cells
65
How are insulin levels in beta cells regulated
Cell membrane had K+ and Ca2+ channels
K+ flows out through channels
When blood glucose conc is high, glucose diffuses into cells
Glucose is metabolised to produce ATP
ATP closes K+ channels
K+ is accumulated, inside becomes less negative
This change opens Ca2+ channels
Ca2+ causes vesicles of insulin to fuse with cell membrane - insulin undergoes exocytosis
66
What is Diabetes mellitus
Disease in which the body is no longer able to control blood glucose conc
Pancreas doesnt produce enough insulin or body cannot respond to insulin produce
67
What is it called when there are very high and very low blood glucose conc
High - hyperglycaemia
Low - hypoglycaemia
68
What is Type 1 diabetes
Patients are unable to produce insulin
Autoimmune response where immune system destroys beta cells
Develops during childhood
69
What is type 2 diabetes and what is it caused by
Patients cannot use insulin to control blood glucose levels
caused by insulin resistance or Beta cells not producing enough
Caused by physical inactivity, excess body weight, overeating of refined carbohydrates
70
How do you treat diabetes
Type 1 - regular glucose monitoring and insulin injections
Type 2 - regulation of carb intake, exercise, weight loss, drugs, insulin injections
71
What are the sources of insulin
extracted from pancreas of pigs, stem cells, genetically engineered bacteria
72
What are the advantages of using genetically modified insulin
produced in pure form - less likely to produce allergic reactions
produced in higher quantities
cheaper
less ethical concerns
73
What are the advantages and disadvantages using stem cell therapy to produce insulin
+No need for donors
+less likely to be rejected
+no need to inject insulin
- Not fully understood
- Concerns that it may cause tumours
- ethical issues
