Nervous & Hormonal Coordination

Homeostasis

Maintaining a constant internal environment/Control, maintenance & regulation of the internal conditions & environment of an organism

Enzymes

Biological catalysts that speed up chemical reactions

Autonomic

Don't require conscious thought

Stimulus

Change in internal/external environment

Effectors

Muscles or glands which bring about a response. They restore optimum levels in the body in response to internal stimuli, or react to an external stimuli to prevent harm

Negative feedback

The action taken by the body to return something to a normal/optimum level following a deviation from that level. It is how the body keeps conditions within it constant at the optimum level (homeostasis). It does the opposite what the stimulus causes.

Receptors

Specialised cells which detect stimuli

Coordination centre

Brain, spinal cord, receive & process information from receptors

Osmoregulation

water control

Thermoregulation

ability to control internal body temperature

High temperature/ low or high pH effect on enzymes

Enzymes denature; active site cannot bind with substrate, enzyme cannot catalyse reactions

If temperature too high

• Thermoreceptors detect rise in temp.

• Thermoreceptors send impulses to hypothalamus

• Hypothalamus send impulses to effectors to lower body temp.

• Hair lies flat; Hair erector muscles relax, prevents pockets of warm air being trapped in them

• Vasodilation; arterioles dilate; increase amount of blood flow to capillaries near skin surface, heat lost by radiation

• Sweating; sweat glands excrete sweat, evaporation of sweat lower body temperature

If temperature too low

• Thermoreceptors detect drop in temperature

• Thermoreceptors send impulses to hypothalamus

• Hair erector muscles contract; traps pockets of warm air around skin, insulates body

• Vasoconstrictions: reduced blood flow to skin surface, reduced radiation of heat from body

• Body shivers; rapid muscle contractions require respiration which produces heat as a byproduct

Effect of low temperature on metabolism

If temperature too low, metabolic reactions become too slow

Nervous & Endocrine system

• Two main systems that control the body

• Autonomic systems (don't require conscious thought)

Nervous system

Consists of CNS & peripheral nervous system. The network of nerve cells which transmit nerve impulses between parts of the body. Information is sent through the nervous system along neurones as electrical impulses.

Endocrine system

The endocrine system secretes hormones into the bloodstream from glands throughout the body. Hormones travel in the blood stream to specific target organs, where they have an effect.

Hormone

A hormone is a chemical messenger that travels in the blood & acts on target cells. They are produced by endocrine glands. In plants, hormones are chemical messengers that affect growth (e.g. auxin)

Glands (7)

• Ovary

• Thyroid

• Testes

• Thymus

• Pancreas

• Adrenal

• Pituitary

Hormones (6)

• Adrenaline

• Testosterone

• Estrogen

• Progesterone

• Insulin

• Glucagon

Sensitivity

The ability to detect & respond to changes in the environment

 

Differences between nervous & endocrine system

Adrenaline

• Produced by adrenal gland (found on top of kidney)

• Prepares body for fight or flight response

• Increases heart rate & breathing rate

Testosterone

• Produced in testes

• Main sex hormone in males

• Development of secondary sexual characteristics in males (hair growth, deeper voice)

Oestrogen

• Produced in ovaries

• Main sex hormones in females

• Development of secondary sexual characteristics in females (breast development) & controls menstrual cycle

Progesterone

• Produced in ovaries

• Maintains pregnancy

• Maintains uterus lining so fertilised egg can implant, & cushions fertilised egg to allow it to develop

Insulin

• Produced by pancreas

• Lowers blood glucose levels

• Converts glucose in blood into glycogen for storage in muscles & liver

Glucagon

• Produced by pancreas

• Raises blood glucose levels

• Converts glycogen into glucose to be released in the bloodstream

Nervous coordination (from stimulus to response)

1. Stimulus causes change in internal/external environment
2. Receptor cells detect the changes 
3. Information is sent from receptors to the co-ordination centre
4. Co-ordination centre processes information & generates a response
5. Co-ordination centre sends instructions to effector
6. Effector carries out response

Sensory neurone

Neurone which carries impulses from receptor cells to the CNS

Motor neurone

Neurone which carries impulses from the CNS to effectors (muscles or glands)

Relay neurone

Neurone which acts as a bridge for the electrical signals between neurones, connects sensory & motor neurones

Neurone

A nerve cell

Synapse

Gap between neurones

Sense, Organs, Stimulus Detected

Synaptic transmissions

the way information is carried between nerve cells

Vesicles

small bags with neurotransmitters inside in presynaptic neurone, fuse with membrane of postsynaptic neurone & release neurotransmitters

What happens to electrical impulses at synapses?

electrical impulses are converted into chemical messengers called neurotransmitters which diffuse across synaptic cleft

Neurotransmitters after use

Neurotransmitters may be taken up by presynaptic neurone and reused, they can be broken down by enzymes within synaptic cleft or recycled in liver

Synaptic transmission process

1. An electrical impulse arrives at the end of one nerve cell (impulse reaches dendrites at end of axon)
2. Neurotransmitters are released into the gap between nerve cells (synaptic cleft)
3. Neurotransmitters diffuse from the first nerve cell (presynaptic neurone) across the gap & bind to receptors on the second nerve cell (postsynaptic neurone)
4. The binding of these neurotransmitters stimulates the second nerve cell (postsynaptic neurone) to generate an impulse.

Reflex Action

Reflex actions are responses that are automatic, unconscious, rapid, & designed to protect the body

Reflex Arc (general)

• Stimuli detected by receptor cells

• Stimulates sensory neurone to carry impulse to CNS

• Relay neurone in CNS passes on response to motor neurone

• Motor neurone stimulates an effector to carry out the response