Unit 2 Biology Revision

Homeostasis

The process by which the body maintains a stable internal environment despite changes in the external environment by detecting stimuli and responding through feedback loops

Types of sensory receptors and their function and stimuli

Parts of a stimulus response model

Effectors can be either

Muscles or glands

Example of feedback loop

Parts of a neuron and their functions

Sensory neuron

Carries signals from sensory receptors to the central nervous system (brain and spinal cord)

Motor neuron

Carries signals from the central nervous system to effectors

Interneuron

Links sensory and motor neurons

Resting membrane potential of a neuron

-70 mV, more Na⁺ ions inside the neuron, more K⁺ ions outside the neuron

Action potential process

To start: Neuron is at resting potential -70 mV

1. Neuron stimulated, Na+ receptor channels open, Na⁺ rushes in

2. Depolarisation - At threshold potential (-55 mV) voltage gated Na⁺ channels open, Na⁺ enters neuron

3. Repolarisation - At +30 mV, Na⁺ channels close, K⁺ channels open, K⁺ diffuses out of neuron

4. Refractory period - Na⁺/K⁺ pump returns neuron to resting potential

Synapse

A junction between two neurons OR a junction between a neuron and a target cell (muscle or gland)

Parts of a synapse

Synaptic transmission process