Homeostasis Flashcards
Conscious response (6 marks)
The stimulus is ……
This is detected by receptors in …
Receptors send an electrical
impulse along a sensory neurone
Sensory neurone sends an electrical impulse along synapse to the brain and spinal cord (CNS)
CNS sends an electrical impulse along a motor neurone
Motor neurone sends an electrical impulse to effector
The effector is a (muscle /gland) in …
The response is (muscle contracts / gland secretes hormones)
Conscious response mnemonic
Some - Stimulus
Really - Receptors
Scary - Sensory neurone
Cops - CNS
Make - Motor neurone
Everyone - Effector
Run - Response
Unconscious response (6marks)
The stimulus is ……
This is detected by (pain/temp) receptors in …
Receptors send an electrical
impulse along a sensory neurone
Sensory neurone sends an electrical impulse along relay neurone
electrical impulse sent along a motor neurone
Motor neurone sends an electrical impulse to effector
The effector is a (muscle) in …
The response is (muscle contracts
Unconscious response mnemonic
Some - Stimulus
Really - Receptors
Sassy - Sensory neurone
Rats - Relay neurone
Make - Motor neurone
Everyone - Effector
Rave - Response
Required practical 4 : reaction time
Person one rests arm over edge of table
Person 2 holds a ruler vertically between thumb and finger
Drop ruler without warning and person 1 must catch it
Repeat twice
Person 1 switches hands and repeats steps
Record time taken to catch ruler
Calculate mean
Adjusting the Iris : Bright light
Iris constricts :
Radial muscle relax
Circular muscle contracts
Adjusting the iris : Dim light
Iris dilates :
Circular muscle relaxes
Radial muscle contracts
Accommodation of a distant object
Light from a distant object over refracts - it doesn’t focus on retina properly
So ciliary muscles relax , causing suspensory ligaments to tighten
Lens becomes thin and refracts light less, focusing it on the retina
Accommodation of a near object
Light from a near object diverges - it doesn’t focus on retina properly
Ciliary muscles contract, causing suspensory ligaments to slacken
Lens becomes thick and refracts light more , focusing it into the retina
HYPEROPIA [long sightedness]
Cannot focus on near object
Light does not bend enough and focuses behind the retina
Caused by incorrect lens shape or eyeball too short
Correcting hyperopia
Use convex lenses
Refract more so they focus on the retina
MYOPIA [short sightedness]
Cannot focus on distant objects
Light bends too much , focusing in front of the retina
Caused by incorrect lens shape or when eyeball is too long
Correcting myopia
Use glasses with a concave lens
Refracts light less so focuses on the retina
When you’re too hot
Sweat produced from sweat gland and evaporates from skin - transfers energy to environment
Blood vessels dilate so more blood flows close to the surface of the skin(vasodilation)
Helps transfer energy to environment
When you’re too cold
Hairs stand up : to trap an insulating layer of air
No sweat
Blood vessels constrict to close off skin blood supply(vasoconstriction)
Shivering : muscle contracts automatically - requires respiration which transfers energy to warm the body
Kidney dialysis
Unclean blood enters dialysis machine from the person . The blood is run alongside a selectively permeable barrier
The barrier is permeable to small molecules - ions,water ,urea
Dialysis fluid contains same concentration of ions & glucose as healthy blood , so substances can only diffuse out of blood if in excess
Waste substances like urea will diffuse across barrier and out of blood
EVALUATING FERTILITY DRUGS
Pros :
- can give an infertile couple a child
Cons:
- Very expensive
-some women have a strong reaction to the hormone ,e.g vomiting
- higher chance of multiple birth -risky for mother and child
HOW IVF WORKS
Woman is giving fertility drug first
FSH matures egg and LH releases egg
Eggs collected from ovary
Eggs mixed with sperm :fertilisation occurs
Fertilised egg divides
Embryo formed
Embryos inserted into woman’s womb/uterus
Adrenaline effects
Increased heart rate
Breaks down glycogen into glucose
Breathing rate increases
Inhibits digestion
Diverts blood away from digestive system
Dilates pupils
Evacuation
Thyroxine regulates :
Thyroxine causes them to rise
Basal metabolic rate
Protein synthesis
Growth and development
Body temperature
Heart rate
Why is Thyroxine releases
In response to TSH (from pituitary gland )
Optimum blood thyroxine regulated by negative feedback
