Topic 9.7-9.9 Eye, Control Of HR, osmoregulation Flashcards
1
Q
What is the fovea?
A
Spot on retina
Where highest number of cone cells found
2
Q
What type of cells are rod and cone cells?
A
Receptor cells
3
Q
Why is the optic nerve the blind spot?
A
No receptor cells there
4
Q
What are the pair of antagonistic muscles in the eye?
A
Ciliary muscles
And
Suspensory ligaments
5
Q
What do both cone and rod cells have in common?
A
- on retina
- are receptor cells
- contain pigments (in disks)(in outer segment of rod and cone cells)
- inner segment has many mitochondria
- both share synapse with bipolar cells
6
Q
What are the differences between rod and cone cells?
A
Rod / cone
Not / colour sensitive
Dim light sensitive / not
More in retina / less
Contain rhodopsin / iodopsin
Can spatial summation w bipolar cell / only 1:1
7
Q
Why does cone cells have high visual acuity but not rod cells?
A
Cone cells have 1:1 ratio with bipolar cell, so higher resolution
Rod cells can spatially summate to converge to bipolar cells so resolution is lower
8
Q
What is the direction of travel of light and action potential?
A
Opposite to each other
Light towards the back of retina
Action pot from back of retina
9
Q
Retinal in rhodopsin is a ___ isomer.
Retinal on its own is a ___ isomer.
A
cis
trans
10
Q
What’s evenly distributed on the retina?
A
rod cells
11
Q
How is rhodopsin converted and what does it convert into?
A
Bleached by light
Into
Trans-retinal and opsin
12
Q
How does trans-retinal and opsin convert into rhodopsin?
A
ATP and enzyme
Takes a long time
13
Q
When is retinal cis and trans?
A
When in rhodopsin, is cis
When alone, is trans
14
Q
What kind of neurotransmitter is glutamate?
A
IPSP
15
Q
Why can’t we see in low light intensities?
A
- not enough light to bleach rhodopsin
- so sodium ion channels open
- glutamate can still be released
- Na+ diffusion, causing rod cell depolarisation and bipolar cell hyperpolarisation
16
Q
Why can’t we see in the dark?
A
- No action potential generated in bipolar cell
- Na+/K+pumps
- Na+ diffuse through
- rod cell depolarises
- glutamate released - is IPSP
- bipolar cell hyperpolarised
17
Q
How can we see in the light?
A
- rhodopsin activated (bleached into trans-retinal and opsin)
- cause cascade of enzyme controlled reactions (cGMP -> GMP -> closing Na+ channels so can’t diffuse and depolarise)
- no glutamate secreted
- rod cell hyperpolarised and bipolar cell depolarised
18
Q
Why must cone cells work at higher light intensities?
A
- contains iodopsin
- needs more light energy to break down bcs it breaks down less readily
19
Q
What are 3 types of cone cells?
A
Red green and blue
20
Q
Where is heart rate controlled?
A
The cardiovascular centre in the medulla oblongata
21
Q
What are the 2 cardiovascular centres in the medulla oblongata?
A
Cardiac accelerator region
And
Cardiac inhibitory region
22
Q
How does heart rate accelerate in terms of the medulla oblongata?
A
In the cardiac accelerator region
- Depolarisation/action potential sent via sympathetic nerve
- nonadrenaline released
- binds to SAN receptors
- increases depolarisation frequency hence HR
23
Q
How does heart rate decelerate in terms of the medulla oblongata?
A
At cardiac inhibitory region
- action potential sent down the vagus nerve
- release acetylcholine to reduce frequency of depolarisation
- HR lowers
24
Q
What type of neurons are vagus and sympathetic nerve?
A
Motor
As it delivers from CNS to effectors
25
How does adrenaline increase HR?
Where from and how is it delivered?
Adrenal gland secrete adrenaline
Via blood
Binds directly to receptors on SAN
26
How do Beta blockers work?
They have similar shape as adrenaline and nonadrenaline
- beta blockers block receptor on SAN
- so adrenaline /nonadrenaline can’t bind
- so no (less) increase of HR
27
What detects pH levels by the medulla oblongata?
Chemoreceptors
28
What detects blood pressure by the medulla oblongata?
Baroreceptors
29
Why is the blood pH levels decreased after exercise?
CO2 released is acidic
30
Explain why many small animals have a heart. (3 marks)
- mass flow
- supply oxygen
- produce blood pressure to support fast movement of blood to cells
- they have high metabolic rate
31
What does myogenic mean? (2 marks)
- stimulation generated within muscle
- results in depolarisation
32
Explain the role of rhodopsin on bipolar cells when light is fallen on the retina. (3-5 marks)
- rhodopsin is bleached to trans-retinal and opsin
- Na+ channels are closed
- Na still moves out
- Rod cell hyperpolarises
- Bipolar depolarises
- **less glutamate released**
33
Explain how pH of blood plasma is affected by heart rate.
Given HR is higher with lower pH from exercise. (4 marks)
- low pH detected by chemoreceptors (from CO2)
- in the cardiac centre of medulla oblongata
- sympathetic nerve sends action potential
- Nonadrenaline released & binds to SAN receptors
- more w.o.es or depolarisation = increase HR
34
Describe the events leading to the release of acetylcholine. (3 marks)
- action potential arrives at presynaptic knob
- calcium channels open and Ca 2+ diffuses in
- vesicles move to membrane
- vesicles fuse with membrane and release acetylcholine
35
Which system is nonadrenaline and acetylcholine released by respectively?
sympathetic (accelerator)
parasympathetic (inhibitory)
36
Why do we need to maintain water concentration in the body?
- prevent cell lysis or crentate (from hypo or hypertonic)
we want isotonic solution
37
Why do we need to control ion conc in the body?
Have enough ions for action potential
38
What are the layers of the kidney from outside in?
capsule
cortex
pyramid
medulla
39
What is the renal pyramid made up of?
renal medulla
40
Where does the ureter lead to?
ureter -> bladder -> urethra
41
How to get rid of excess amino acids in the liver?
step 1: deamination
amino acids + O2 -> keto acids + ammonia
step 2: ornithine cycle
ammonia + CO2 -> urea
42
Why is ammonia bad/not good for us?
toxic and soluble
43
How does urea in liver travel to the kidney?
via blood
44
What are the 5 processes in nephron and where do they take place?
1. ultrafiltration - glomerulus/bowman's capsule
2. selective reabsorption - PCT
3. water conservation - loop of Henle
4. ion & pH regulation - DCT
5. water reabsorption - PCT?
45
What are the 5 filtrates (molecules that get pushed out) in nephron?
ions
water
glucose
amino acids
urea
46
What happens in ultrafiltration?
in glomerulus + Bowman's capsule
- small molecules forced out of blood
- from glomerulus to Bowman's capsule
- due to high pressure
47
Why is there high pressure in ultrafiltration?
Lumen of Afferent arteriole is wider than Efferent arteriole
(also hydrostatic pressure from heart contractions)
48
What happens in selective reabsorption?
In PCT,
- glucose and amino acids 100% reabsorbed
- some ions, water reabsorbed
- no urea reabsorbed
49
What does PCT and DCT stand for?
Proximal Convoluted Tube
Distal Convoluted Tube
50
Why is 100% glucose reabsorbed?
Useful for respiration!
51
In what conditions would glucose not be 100% reabsorbed in nephrons?
Kidney failure or diabetes
52
What is urine made up of? 2 main things
urea
excess water and ions
53
What are the 3 layers in Bowman's capsule? (top to bottom)
- capillary endothelium (one cell thick)(with pores)
- basement membrane (mesh of collagen)
- podocyte
54
What is the basement membrane made up of?
meshwork of collagen and glycoprotein fibres
55
What is the movement of glucose in the nephron?
- passes out in glomerulus (by high pressure)
- reabsorbed in PCT (by active transport)
56
How is glucose selectively reabsorbed in the PCT?
Via active transport
57
Describe how urea is produced in mammals. (2 marks)
deamination - where amino group is removed from amino acids
- amino acids + O2 -> ammonia + keto acids
ornithrine cycle produces urea
- ammonia + CO2 -> urea
58
Describe how exercise leads to the stimulation of the cardiac centre in the medulla oblongata. (4 marks)
- exercise increases respiration rate
- increasing CO2 conc in blood
- blood pH decreases
- detected by chemoreceptors
- in aorta
- impulses sent to cardiac centre in medulla oblongata
59
Where are chemoreceptors found?
Aorta
60
What are 3 adaptations of the PCT?
Proximal convoluted tube
1. **Many mitochondria** to provide ATP for active transport of glucose/amino acids
2. **Microvilli** provide large SA
3. Many **carrier proteins** for glucose and amino acids
61
How are molecules transported in and out of the PCT?
Ions by Facilitated diffusion, **active transport** and co-transport
Water by osmosis (60%)
Urea by diffusion
62
How are carrier proteins used for glucose and amino acid transport in PCT?
1. Na+ **actively transported** out of cells to tissue fluid (using ATP)
2. Glucose or amino acid enter cells with sodium ions by **active transport**
3. Glucose and amino acid diffuses into blood capillary
63
What takes place at the loop of Henle?
Water conservation
64
What is the permeability of the loop of Henle?
permeable in the descending limb
impermeable in ascending
65
Where is the loop of Henle and collecting duct?
in medulla
66
What are the adaptations in the loop of Henle to aid water conservation?
counter current multiplier with capillaries in medulla
67
Explain the counter current multiplier in loop of Henle for water conservation
- Na+ and Cl- **actively** pumped out ascending limb
- WP in medulla decreases
- water travel from descending limb to capillaries/medulla via osmosis
- Na+ enter descending limb
- urea conc increases in loop of H
68
How would the loop of henle adapt to desert animals?
- longer / bigger
- to have steeper conc gradient
- so more ions actively transport into capillaries
- lowers wp in blood
- so more water enter blood via osmosis
= reabsorb / conserve more water
69
does descending or ascending limb have higher water potential?
descending
70
Where does regulation of ions hence pH take place?
Distal Convoluted Tube
DCT
71
What happens in the Distal Convoluted Tube? (DCT)
regulates ions such as
H+ / OH- / HCO3^-
other useful ions like Cl- , Mg2+ , Na+ also reabsorbed from filtrate
72
What happens in the collecting duct on a hot day?
- decreased wp in blood
- detected by osmoreceptors in hypothalamus
- hypo. sends more action pot to pituitary gland
- secrete more ADH = more permeable
- so more water reabsorbed into capillaries by osmosis
= urine more concentrated and smaller volume
73
How does ADH secreted increase permeability?
- more aquaporins
- act as water channels - made of proteins
- released by vesicles by exocytosis
74
Where are aquaporins found?
embedded in collecting ducts
75
What happens in the collecting duct on a cold day?
- increased water potential in blood detected by ...
- **less** action potentials sent to pituitary gland
- **less** ADH secreted
- lowers permeability, **less** aquaporins, less water reabsorbed into capillaries by os
- urine more diluted and larger vol
76
What are ectotherms?
organisms require external sources of heat / behaviour mechanisms to keep warm
77
What are endotherms?
Has homeostasis to regulate own temp
internal corrective mechanism and behaviour
78
What happens if the receptors in hypothalamus detect body temp that is too cold and hot?
too hot - sweat, vasodilation
too cold - vasoconstriction, hair stands up, shivering
79
Explain the mechanisms to being too cold
vasoconstriction
- reduce heat loss, shunt vessels dilate
hairs stand up
- trap insulating layer of air
shivering
- muscles contract
- increase respiration and exothermic reaction
- heat thermal energy released in this process
80
How does vasodilation help cool the body down?
- vasodilation of arterioles
- heat loss by radiation
- more blood to capillaries closer to the skin surface
81
Explain how the loop of Henle is involved in the production of concentrated urine. (5 marks)
- Na+ / Cl- ions move out of ascending limb by **active transport**
- ascending limb is impermeable to water
- descending limb is permeable to water
- results in lower WP in **medulla**
- counter current multiplier mechanism
- water moves out of descending limb into blood by osmosis
- water moves out of collecting duct by osmosis
82
Explain how tissue fluid is returned to capillaries. (3 marks)
- when oncotic pressure is greater than hydrostatic pressure
- oncotic pressure generated by plasma proteins
- there is more protein in plasma than tissue fluid
- plasma proteins are too large to pass out of capillaries
83
Describe how the stimulation of the hypothalamus leads to the production of concentrated urine. (3 marks)
- osmoreceptors in hypothalamus detects low blood WP
- action potentials sent to the pituitary glands to release ADH
- ADH increases permeability of collecting duct as causes more aquaporins
- more reabsorption of water into blood
84
85
Wheee is glucose 100% selective reabsorbed? How?
By active transport
In the proximal tubule
86
What is the mechanism used in the loop of Henle?
COUNTER CURRENT MULTIPLIER
