Bio Unit 2

Homeostasis

The process by which organisms maintain a stable internal environment despite changes in external conditions

Stimulus-Response Model

Stimulus —> Receptor —> Control Centre —> Effector —> Response

Two types of effectors

Muscles and Glands

What does a muscle effector do

Contract to produce movement or generate heat

What does a gland effector do

Secrete substances such as hormones or enzymes

Negative feedback

A mechanism that reduces the effect of the initial change to bring the system back to normal

Characteristics of the nervous system

Neurons, messenger is electrical signal, carried by neurons, message is released close to the cell of influence, message is sent to specific cell/tissue, very quick and short

Characteristics of the endocrine system

Gland cells, messenger is hormones, carried by blood stream, message is released distant to the cell of influence, message is sent to the entire body, is slow and long

Chemoreceptors

Detects changes in chemical composition

Thermoreceptors

Detects changes in temperature

Mechanoreceptors

Detects physical pressure, stretch, vibration, or movement

Photoreceptors

Detects light

Nociceptors

Detects tissue damage or potentially harmful stimuli

Description and Function of Dendrites

Short branching extensions from soma, receives signals from other neurons/sensory receptors

Description and Function of Cell Body (Soma)

Contains nucleus and organelles, integrates incoming signals, supports cell metabolism

Description and Function of Axon

A long, slender projection extending from soma, transmits electrical impulses from cell body to effectors

Description and Function of Myelin Sheath

Fatty insulating layer surrounding axon (made up of Schwann cells), increases speed of impulse conduction by insulating axon

Description and Function of Nodes of Ranvier

Gaps between myelin sheath segments along axon, allow impulses to jump from node to node (speed transmittion)

Description and Function of Axon Terminal

Distant end of axon (often branched), transmits the impulse to next neuron or effector

Description and Function of Synapse

Junction between two neurons/neuron and an effector, allows communication via neurotransmitters across small synaptic gap

Label the neuron:

Three types of neurons

Sensory Neuron, Interneuron, Motor Neuron

Sensory Neuron

Transmits information from sensory receptors to central nervous system

Interneuron

Processes information and relays signals between sensory and motor neurons within the CNS

Motor Neuron

Sends signals from the CNS to effectors

Central Nervous System

Only brain and spinal cord

Peripheral Nervous System

All nerves other than brain and spinal cord

Sensory Neuron

Interneuron

Motor Neuron