Topic 9.7-9.9 Eye, Control Of HR, osmoregulation Flashcards
What is the fovea?
Spot on retina
Where highest number of cone cells found
What type of cells are rod and cone cells?
Receptor cells
Why is the optic nerve the blind spot?
No receptor cells there
What are the pair of antagonistic muscles in the eye?
Ciliary muscles
And
Suspensory ligaments
What do both cone and rod cells have in common?
- 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
What are the differences between rod and cone cells?
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
Why does cone cells have high visual acuity but not rod cells?
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
What is the direction of travel of light and action potential?
Opposite to each other
Light towards the back of retina
Action pot from back of retina
Retinal in rhodopsin is a ___ isomer.
Retinal on its own is a ___ isomer.
cis
trans
What’s evenly distributed on the retina?
rod cells
How is rhodopsin converted and what does it convert into?
Bleached by light
Into
Trans-retinal and opsin
How does trans-retinal and opsin convert into rhodopsin?
ATP and enzyme
Takes a long time
When is retinal cis and trans?
When in rhodopsin, is cis
When alone, is trans
What kind of neurotransmitter is glutamate?
IPSP
Why can’t we see in low light intensities?
- 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
Why can’t we see in the dark?
- No action potential generated in bipolar cell
- Na+/K+pumps
- Na+ diffuse through
- rod cell depolarises
- glutamate released - is IPSP
- bipolar cell hyperpolarised
How can we see in the light?
- 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
Why must cone cells work at higher light intensities?
- contains iodopsin
- needs more light energy to break down bcs it breaks down less readily
What are 3 types of cone cells?
Red green and blue
Where is heart rate controlled?
The cardiovascular centre in the medulla oblongata
What are the 2 cardiovascular centres in the medulla oblongata?
Cardiac accelerator region
And
Cardiac inhibitory region
How does heart rate accelerate in terms of the medulla oblongata?
In the cardiac accelerator region
- Depolarisation/action potential sent via sympathetic nerve
- nonadrenaline released
- binds to SAN receptors
- increases depolarisation frequency hence HR
How does heart rate decelerate in terms of the medulla oblongata?
At cardiac inhibitory region
- action potential sent down the vagus nerve
- release acetylcholine to reduce frequency of depolarisation
- HR lowers
What type of neurons are vagus and sympathetic nerve?
Motor
As it delivers from CNS to effectors
How does adrenaline increase HR?
Where from and how is it delivered?
Adrenal gland secrete adrenaline
Via blood
Binds directly to receptors on SAN
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
What detects pH levels by the medulla oblongata?
Chemoreceptors
What detects blood pressure by the medulla oblongata?
Baroreceptors
Why is the blood pH levels decreased after exercise?
CO2 released is acidic
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
What does myogenic mean? (2 marks)
- stimulation generated within muscle
- results in depolarisation
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
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
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
Which system is nonadrenaline and acetylcholine released by respectively?
sympathetic (accelerator)
parasympathetic (inhibitory)
Why do we need to maintain water concentration in the body?
- prevent cell lysis or crentate (from hypo or hypertonic)
we want isotonic solution
Why do we need to control ion conc in the body?
Have enough ions for action potential
What are the layers of the kidney from outside in?
capsule
cortex
pyramid
medulla
What is the renal pyramid made up of?
renal medulla
Where does the ureter lead to?
ureter -> bladder -> urethra
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
Why is ammonia bad/not good for us?
toxic and soluble
How does urea in liver travel to the kidney?
via blood
What are the 5 processes in nephron and where do they take place?
- ultrafiltration - glomerulus/bowman’s capsule
- selective reabsorption - PCT
- water conservation - loop of Henle
- ion & pH regulation - DCT
- water reabsorption - PCT?
What are the 5 filtrates (molecules that get pushed out) in nephron?
ions
water
glucose
amino acids
urea
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
Why is there high pressure in ultrafiltration?
Lumen of Afferent arteriole is wider than Efferent arteriole
(also hydrostatic pressure from heart contractions)
What happens in selective reabsorption?
In PCT,
- glucose and amino acids 100% reabsorbed
- some ions, water reabsorbed
- no urea reabsorbed
What does PCT and DCT stand for?
Proximal Convoluted Tube
Distal Convoluted Tube
Why is 100% glucose reabsorbed?
Useful for respiration!
In what conditions would glucose not be 100% reabsorbed in nephrons?
Kidney failure or diabetes
What is urine made up of? 2 main things
urea
excess water and ions
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
What is the basement membrane made up of?
meshwork of collagen and glycoprotein fibres
What is the movement of glucose in the nephron?
- passes out in glomerulus
- reabsorbed in PCT
How is glucose selectively reabsorbed in the PCT?
Via active transport
Describe how urea is produced in mammals. (2 marks)
- deamination - where amino group is removed from amino acids
- ammonia combines with carbon dioxide
- ornithrine cycle produces urea
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
Where are chemoreceptors found?
Aorta
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
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
How are carrier proteins used for glucose and amino acid transport in PCT?
- Na+ actively transported out of cells to tissue fluid (using ATP)
- Glucose or amino acid enter cells with sodium ions by active transport
- Glucose and amino acid diffuses into blood capillary
What takes place at the loop of Henle?
Water conservation
What is the permeability of the loop of Henle?
permeable in the descending limb
impermeable in ascending
Where is the loop of Henle and collecting duct?
in medulla
What are the adaptations in the loop of Henle to aid water conservation?
counter current multiplier with capillaries in medulla
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 reabsorbed from descending limb via osmosis
- Na+ enter descending limb
- urea conc increases in loop of H
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
does descending or ascending limb have higher water potential?
descending
Where does regulation of ions hence pH take place?
Distal Convoluted Tube
DCT
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
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
How does ADH secreted increase permeability?
- more aquaporins
- act as water channels - made of proteins
- released by vesicles by exocytosis
Where are aquaporins found?
embedded in collecting ducts
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
What are ectotherms?
organisms require external sources of heat / behaviour mechanisms to keep warm
What are endotherms?
Has homeostasis to regulate own temp
internal corrective mechanism and behaviour
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
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
How does vasodilation help cool the body down?
- vasodilation of arterioles
- heat loss by radiation
- more blood to capillaries closer to the skin surface
