Homeostasis and nervous system (Chapter 8)

Feedback systems maintain homeostasis

Three components: Sensor, control centre, effector

Sensor: detects changes in the internal environment and sends a signal to a control centre

Control Centre: received information frim sensors and sends out signals and sets the range of values within which the variable must be in.

Effector: receives signals from the control centre and responds to change the internal variable

Two kinds: negative and positive feedback systems

negative: the body works to reverse a change detected in a variable so that the variable is brought back within a normal range

Feedback loop stops when variable is restored to normal conditions

Positive feedback systems tends to strengthen or increase a change in a variable. Stops when "GOAL" is reached

Example: Childbirth, blood clotting

Literary Work

Homeostasis is maintained through feedback systems that continually monitor, assess, and adjust variables in the body’s internal environment.

Central Nervous System- brain and spinal cord and associated nerves.
This integrates and processes info sent by nerves

Peripheral Nervous System- network of nerves that carry sensory messages to the CNS and send info from the CNS to the muscles and glands
Contains autonomic and somatic nervous systems

Homeostasis is maintained in the body by the actions of the sympathetic and parasympathetic nervous systems.

In general, the sympathetic nervous system prepares the body for fight-or-flight, while the parasympathetic system returns the organs to a resting state.

Neuron- nerve cell, the structural and functional unit of the nervous system. They respond to physical and chemical stimuli, and conduct electrochemical signals and release chemicals that regulate body processes.

Nerve- message pathway of the nervous system, made up of many neurons grouped into bundles and surrounded by protective connective tissue.

Glial cell- support cell of nervous system that nourishes neurons, removes their wastes, defends against infection, and provides a supporting framework for all the nervous system tissue.

Myelin sheath- the fatty, insulating layer around the axon of a nerve cell, composed of Schwann cells. It protects myelinated axons and speeds up the rate of nerve impulses.
See Table 8.1, page 352 for different types of neurons (multipolar, bipolar, unipolar)

Network of nerves

It carries sensory messages to the central nervous system (CNS)

And sends information from the CNS to the muscles

Somatic system

Under voluntary control

carries information to and from skin and skeletal muscles (via sensory neurons and motor neurons)

Autonomic system

autonomic or involuntary vontrol

internal reaction to s situation

activated in stressful situations

also referred to as the 'fight or flight' situations

Activated when the body is calm and at rest

"rest and digest" response

Sensory neuron sensory receptors (on skin) receive stimuli and form a nerve impulse, and transmit impulses to the CNS

Interneuron- found in CNS (spinal cord) and link sensory and motor neurons

Motorneuron- motor neurons transmit info from CNS to effectors (muscles, glands and other organs)

• All cells have a membrane potential, but the neuron is unique in that it can change the potential of its membrane to generate an impulse. An impulse is transmitted from one neuron to the next by neurotransmitters at a synapse

Daniel Defoe - Robinson Crusoe

Literary Work

The brain can be subdivided into three general regions: the hindbrain, the midbrain, and the forebrain.

The outer layer of the cerebrum, called the cerebral cortex, is composed of grey matter, and is thought to be the source of human intellect.

The right and left halves of the cerebral cortex are made of four pairs of lobes, each of which is associated with particular functions.