Coordination and Control

Stimulus

is a change in the internal or external environment of an organism that initiates a response

Response

is a change in an organism or part of an organism which is brought about by stimulus

Receptor

is the part of the organism that detects the stimulus

Effector

is the part of an organism that responds to the stimulus

Differences in the Nervous and Endocrine System

Nervous:

• messages are carried as electrical impulses along nerves

• messages are transmitted rapidly

• messages are carried to precise places in the body

Endocrine System:

• messages are carried by chemicals (hormones) in the blood

• messages are usually transmitted slowly

• messages are carried to generalized regions of the body

The Nervous System

The human nervous system is composed of neurons or nerve cells and is divided into two parts

1. the central nervous system, which consists of the brain and spinal cord

2. The peripheral nervous system, which consists of cranial and spinal nerves that connect the central nervous system to all parts of the body. Autonomic nervous system, voluntary or somatic nervous system

The Brain

1. Cerebrum - controls conscious thought, coordinates voluntary actions, responsible for intelligence, memory

2. Cerebellum - controls balance and posture, coordinates movement

3. Medulla oblongata - controls automatic, involuntary actions (heart rate and breathing rate)

4. Hypothalamus - regulates body temperature, regulates the concentration of body fluids by controlling the release of ADH

5. Pituitary Gland - secretes a variety of hormones, ADH.

Nuerons

are specialized cells that conduct nerve impulses throughout the nervous system. The three types of neurons are:

1. Sensory Neurons, which transmit impulses from receptors to the CNS

2. Motor Neurons, which transmit impulses from the CNS to effectors

3. Relay Neurons, which transmit impulses throughout the CNS, They link sensory and motor neurons

Nerves

Nerves are cordlike bundles of nerve fibres of neurons surrounded by connective tissue through which impulses pass between the CNS and the rest of the body. they can be classified into two types based on where they connect to the CNS:

• Cranial nerves connected to the brain

• Spinal nerves connected to the spinal cord

Synapses

Adjacent neurones do not touch. There are tiny gaps called synapses. Electrical impulses cannot pass so they are converted into chemical signals in the form of neurotransmitters in order to cross the synapse. As they reach the other neuron, they are converted back into electrical impulses.

Voluntary Actions

is an action that is consciously controlled by the brain. The cerebrum of the brain initiates voluntary actions in one of two ways, both of which involve conscious though, it can coordinate incoming information from sensory neurons and initiate an action or it can spontaneously initiate an action without receiving any incoming information.

Involuntary Actions

is an action that occurs without consciously without thought.

Involuntary actions:

• are not learned are rapid

• are simple because the same response always results from the same stimulus.