Biology YEAR 12 Module 8

What is Homeostasis?

The constant regulation and changes in the body to maintain a stable internal environment

Key characteristics of the Nervous system

• Fast and Precise

• Electrical Impulses

• Responds quickly

Homeostasis Process (steps) 

• Stimulus

• Receptor

• Control centre 

• Effector 

• Response

Human responses to increased body temperature

• Dilated blood vessels 

• Sweat glands 

• Metabolic rate decreases 

Human responses to decreased body temperature

• Constricted blood vessels

• Hair erector cells

• Shivering

• Increased metabolic rate

Body response to HIGH blood glucose

• Releases insulin from pancreas

• Insulin binds to cells

• Insulin indicates cells to take up more glucose

Body response to LOW blood glucose

• Pancreas ALPHA cells release Glucagon

• Liver converts glucagon → glucose

Endotherms

An organism capable of maintaining constant internal temperature

Ectotherm

Organisms that rely on external temperature to warm up

Structural adaptation

Adaptation to the physical outside features: e.g: Giraffe Neck

Behavioural adaptation

Adaptation of behaviour of an organism: Grazing in herds

Physiological adaptation

Adaptation to the internal systems: Sweating, hybernation

Neurons

cells of the nervous system

Motor Neurons Purpose

Responsible for transmitting electrical signals from CNS to muscles/glands

Sensory Neurons Purpose

Responsible for transmitting detection of stimuli to CNS 

Parts of central nervous system (CNS)

Brain and spinal cord

Parts of the peripheral nervous system (PNS)

Everything but the Brain and Spinal cord

Interneurons Purpose

Transmitting messages from sensory neurons to motor neurons 

How does the electrical impulse go to the next neuron?

Converted into neurotransmitter across synapse

What is polarisation

The resting stage of a neuron (-70mV)

what is depolarisation

Neuron is disrupted, causing NA+ gates to open, flooding neuron with positive sodium ions

what is repolarisation

The active transport of K+ ions back into the neuron to restabilise to -70mV

Purpose of Axons

Transmits signals down myelin sheath towards axon terminal

Purpose of dendrites

Receive signals from other neurons

Purpose of Myelin sheath

Speed up electrical signal

Purpose of Axon Terminal

transmit signal to next neuron.

What is hyperpolarisation

The neuron is too negative preventing multiple signals firing

What is the thyoid gland responsible for

Releasing thyroxine, responsible for regulating metabolic rate

What does the adrenal gland do?

Trigerred by SNS, releases adrenaline for fight or flight response

What does the Pituitary gland do

“the master gland” releases hormones that control other glands

What do the testes do?

Release testosterone, stimulate development of male sex characteristics, increase muscle mass, promote sperm production

What do the ovaries do?

Release oestrogen + Progesterone, stimulates development of female sex characteristics, inhibits further ovulation during pregnancy, maintains uterial lining after ovulation

What does the pancreas do

Regulate blood glucose via insulin production

How does insulin reduce blood glucose

Insulin attaches to cells and encourages ingestion of glucose

How does glucagon increase blood glucose

Released by pancreas and converted into glucose by liver