Lesson B1 - PHYSIOLOGICAL AND PHARMACOLOGICAL ASPECTS OF THE CENTRAL AND PERIPHERAL NERVOUS SYSTEM Flashcards
The nervous system can be divided into two main components
the central nervous system (the brain and spinal cord) and the peripheral nervous system
afferent or sensory nerve fibres which carry messages to the brain, and efferent nerve fibres which carry messages
from the brain and spinal cord to tissues.
The efferent system is divided into motor nerves which innervate skeletal muscle, and
the autonomic nervous system.
The central nervous system (CNS) controls
all bodily functions
It consists of a central part, the
brain and spinal cord, linked to
a peripheral part, nerve fibres
The sensory nerve fibres carry
messages from tissues to the brain or spinal cord, and the motor nerve fibres carry messages
from the brain or spinal cord to the tissues.
Three main parts of the brain
- Forebrain
- Midbrain
- Hindbrain
The forebrain: cerebral cortex =
This is the largest part of the brain which is very rich in nerve cells. It is composed of grey matter (outside) and white matter (inside); it is divided
into lobes or regions, each with specific functions
The forebrain: Thalamus:
A relay centre; from here impulses are relayed to the cerebral cortex
The forebrain:Hypothalamus:
A very important area; consists of various specialized regions of nuclei
located near the base of the skull. The functions are to control the involuntary functions of
the body that are necessary for living, e.g. regulation of heart, blood pressure, body
temperature, and metabolism
The forebrain: Pituitary
A small gland located at the base of the brain which secretes hormones that
control growth, behaviour and metabolism of the body through the action of these
hormones on peripheral tissues
The Midbrain
The midbrain is the area that links the forebrain with the hindbrain.
The Hindbrain
Medulla (the bulb): This is the site of origin of many cranial nerves. It is where
regulation of respiration (breathing centre) and regulation of heart and blood pressure
occurs
Cerebellum: The cerebellum is a large, highly convoluted structure connected to the brain
stem by large fibre tracts. It is responsible for coordination and posture
The functional unit of the brain
is the neuron
each nerve cell or neuron has three
parts:
The cell body or soma contains a nucleus and surrounding cytoplasm which is packed with
rough endoplasmic reticulum, a network of smooth endoplasmic reticulum, and abundant
vesicles which can be secreted.
The dendrites function as the receiving antennae for incoming information, are usually
short, and can have highly complex branching patterns.
The axon, a single fibre that extends from the cell body and ends at a synapse. The axon
carries signals away from the cell body.
In order for the brain to function properly, the nerve cells (neurons)
must communicate with each
other.
The junction between two neurons is called the
synapse
The synapse is commonly formed by contact of the
axon belonging to one neuron with a dendrite or
the cell body of another neuron.
The passage of a signal from one neuron to
another neuron is called
synaptic transmission
Synaptic transmission is usually
chemical in nature
Substances mediating synaptic transmission are
synaptic transmitters
In chemical transmission, the
release of a transmitter substance is required in order to
activate the other cell or pass on the
message.
The nerve impulse (electrical activity) passes down a nerve axon and releases
a chemical substance into the synaptic cleft.
The postsynaptic membrane contains binding sites for the
chemical transmitter. These binding sites are called
receptors