B7. Co-ordination and response
Nervous control in humans
Human nervous system
CNS (brain and spinal cord) - Co-ordination
Peripheral nervous system (rest of body) - Co-ordinating/regulating bodily functions
Human eye
- Light enters through pupil
- Cornea and lens focus image
- Flipped image projected on retina wall
Simple reflex arc
Reflex - Automatic action that isn't learned e.g. blinking when something flies towards face
Reflex only goes to spine, not brain
- Pain sends impulse down sensory neurone
- Impulse ravels through into spinal nerve
- Impulse travels along relay neurone, into motor neurone
- Impulse travels down axon of motor neurone
- Impulse causes muscle to contract (or do something else)
Hormones
What is a hormone?
Chemical substance
Produced by gland
Carried by blood
Alters activity of one or more organs
Destroyed by liver afterwards
Adrenaline
Released when you're excited or frightened
Faster heart beat
Muscles get oxygen quicker
Digestive system slows down (butterflies in stomach)
Nervous system vs Endocrine (hormonal) system
Made up of: neurones vs secretory cells
Info transmitted as: electrical impulses vs chemicals called hormones
Transmitted in: Nerve fibres vs chemicals dissolved in blood plasma
Info travels: Very quickly vs slowly
Effects last: Short time vs longer
Tropic responses
Geotropism: Plant's response to gravity
Phototropism: Plant's response to light
In shoots
Auxin (plant hormone) makes plant grow faster
Positive phototropism: Plant grows towards light
Negative geotropism: Plant grows against gravity (up)
In roots
Auxin makes plant grow slower
Negative phototropism: Roots grow away from light
Positive geotropism: Plant grows in direction of gravity (down)
Homeostasis
Maintenance of a constant internal environment
Skin structure
Hair
Sweat gland (under skin, next to hair)
Temperature recpetors
Blood vessels
Fatty tissue
Vasodilation (too hot)
Blood vessels near skin widen
Warm blood closer to surface, loses heat
Skin hair muscles relax, hairs go flat
Sweat
Sweat evaporates
Heat energy used, we cool down
Vasoconstriction (too cold)
Blood vessels thin, blood loses less heat near surface
Hair muscles contract
No sweat released
Hairs trap warm air close to skin
Muscles contract and relax (shivering), requiring respiration
Respiration generates heat
Blood sugar levels
Brain detects quantity of glucose in blood
If there's too much (hyperglycemia)
Brain sends message to pancreas
Pancreas produces insulin (hormone), detected by liver
Liver stores glucose as glycogen
Blood sugar normalised, message disappears
If there's too little (hypoglycemia)
Brain sends message to pancreas
Pancreas produces glucagon (hormone), detected by liver
Liver converts glycogen back to glucose
Blood sugar normalised, message disappears
Glycogen - Stored glucose in liver
Insulin - Hormone for high blood sugar
Glucagon - Hormone for low blood sugar
Negative feedback - Stop making a change when normality is achieved