Basic Psychology
PYC1501
University of South
Africa
Study Guide
Summaries
, Human Nervous system
The human nervous system is divided into two different systems that interact with one another.
• The Peripheral Nervous system – controls
volitional (somatic) and non-volitional
(autonomic) behaviours using cranial and
spinal nerves.
• The Central nervous system – consists of
the brain stem, and the spinal cord. Each
division performs a variety of tasks
The peripheral nervous system
The peripheral nervous system carries the signals necessary for the body to survive and some of the signals are related to voluntary actions. The
peripheral nervous system is divided into somatic and autonomic nervous systems.
- The somatic nervous system;
This system is associated with conscious and voluntary activities. It is involved in the relay of sensory and motor
information to and from the central nervous system. It consists of motor and neurons and sensory neurons.
➢ The motor neurons that carry information from the CNS to the muscles, are called efferent neurons
➢ The sensory neurons that carry information to the CNS are called afferent neurons.
Each nerve is basically a two-way process containing thousands of both efferent and afferent neurons.
- The autonomic nervous system;
The autonomic nervous system controls involuntary functions of our internal organs and glands. It is divided into the
sympathetic and parasympathetic divisions.
➢ The Sympathetic nervous system is involved in preparing the body for stress related activities
➢ The Parasympathetic nervous system is associated
with returning the body to routine, day-to-day Homeostasis is a state of equilibrium, in
operations. Therefore, the parasympathetic nervous which biological conditions are
system restores and calms down the physiological maintained at optimal levels
responses so as to maintain homeostasis
The central nervous system
This system mainly performs the “information synthesising” function. During this process, the brain and spinal cord use appropriate motor
output, which is based on the type of sensory input.
The CNS controls everything from organ function and high level thought to purposeful body movement. It is the control centre of the body.
The brain and the spinal cord communicate largely by sending electrical signals through individual nerve cells that make up the fundamental
building blocks of the nervous system called neurons. There are approximately 100 billion neurons in the human brain and each has many
contacts with other neurons.
, ❖ The Brain
The brain is the headquarters of the entire nervous system where activities such as sensation, perception, thinking, emotions and
planning take place. The limbic system, consists of highly specialised neural structures that are located at the top of the brainstem.
These structures are involved in regulating emotions and they include the hippocampus, amygdala, the thalamus, the insula cortex,
the anterior cingulate cortex, and the prefrontal cortex. These structures influence fear and aggression, the sleep-wake cycle, sexual
desires and even memory.
The cerebellum is situated at the back of the brain. It coordinates actions
without the need for any conscious awareness. The cerebrum (which includes
the cerebral cortex) is regarded as the most advanced portion of the brain.
Inside the cerebral cortex, the gray matter (neural cell bodies) lies outside and
the white matter (myelinated axons) lies inside. The cerebral hemispheres
oversee the types of processes that are associated with more awareness and
voluntary control, such as speaking and planning. Thy contain our primary
sensory areas; seeing, hearing, feeling and moving. These two hemispheres are
connected to one another by a thick bundle of axons called the corpus
callosum. The brain is contralateral, meaning that the left side of the brain is
responsible for controlling a number of sensory and motor functions of the
right side side of the body, and vice versa.
The frontal lobe controls important cognitive functions. The parietal lobe is primarily responsible for the whole body receiving inputs
from the skin and the muscles. This means that a touch in the skin activates the parietal lobe. The occipital lobe contains the primary
visual cortex that is responsible for vision. The temporal lobe contains auditory and offactory regions. This means that auditory and
smell sensations are activated through the temporal lobe.
If we were to cut the brain in half, a new set of structures come into view. These structures perform different functions.
1. The limbic system contains a number of nuclei that process memory (hippocampus and fornix), emotions and attention (cingulate
gyrus)
2. The globus pallidus is involved with motor movements and their coordination.
3. The hypothalamus and thalamus are involved with drives, motivations, and trafficking of sensory and motor throughputs. The
hypothalamus also plays a key role in regulating the endocrine hormones in conjunction with the pituitary gland that extends from
the hypothalamus.
4. The midbrain comes into view with superior and inferior colliculi, which process visual and auditory information,mass does the
substantia nigra
5. The reticular formation regulates sleep, arousal and temperature.
, 6. The hindbrain with the pins processes sensory and motor information using the cranial nerves. It serves as a bridge that connects the
cerebral cortex with the medulla, and reciprocally transfers information back and forth between the brain and the spinal cord
7. The medulla oblangata processes breathing, digestion, heart and blood vessel function, swallowing, and sneezing.
8. The cerebellum controls motor movement coordination, balance, equilibrium and muscle tone
The midbrain and the hudnbrain (make up the brain stem) culminate in the spinal cord. Paired nerves, called ganglia, exit the spinal cord;
▪ Dorsal nerves (afferent) receive sensory information from the skin and muscles.
▪ Ventral nerves (efferent) send signals to muscles and organs to respond.
❖ The brainstem
The brainstem is located at the top of the spine and the bottom of the brain. It oversees a wide range of very basic life support
functions for the body – including breathing, digestion, and the heartbeat.
❖ The spinal cord
The spinal cord connects with the brain and brain stem to all of the major nerves in the
body. Spinal nerves originate from the spinal cord and control the functions of the rest of the
body. Impulses are sent from receptors through the spinal cord to the brain, where they are
processed and synthesised into instructions. This data is sent back through the spinal cord to
muscles and glands for motor output.
Impulse conduction in the neuron
A neuron is a cell in the nervous system that receives and transmits information. It is made up four major
parts:
- Dendrites; branching tree like fibres that collect information from other neurons
- A cell body (soma); contains the nucleus of the cell and keeps the cell alive
- An axon; a segmented fibre that sends the information to another neuron or to the muscles and glands
- The terminal boutons; branches that release information as the synapse to other adjacent neurons
Some neurons have hundreds or even thousands of dendrites, and these dendrites may themselves be branched to allow the cell to
receive information from thousands of other cells. The axons are also specialised, such as those that send messages from the spinal
cord to the muscles in the hands or feet, may be very long ‐ even up to several feet in length.
To improve the speed of communication and to keep the electrical charges from shorting out
The myelin sheath is a layer of fatty tissue with other neurons, axons are often surrounded by a myelin sheath.
surrounding the axon that acts as an insulator and Axons branch out toward the end, forming the terminal buttons.
allows faster transmission of the electrical signal However, some neurons are not covered in sheaths and therefore, they are unmyelinated.
Signal information in these neurons travels much slower than in myelinated neurons.
When the dendrites channel information to the soma, it builds up as an electro‐chemical signal. This electrical part of the signal,
called an action potential travel down the axon, a long tail that leads away from the soma and toward the next neuron. When people
talk about the ‘nerves’ in the nervous system, they typically refer to bundles of axons that form long neural wires along which
electrical signals can travel.
❖ Action Potential
An action potential is an all‐or‐nothing event that occurs when there is a change in the charge or potential of the cell from its
resting membrane potential. An all‐or‐nothing event simply means that a neuron will either fire an impulse signal or not at all.
There is no halfway or in‐between these possibilities. To initiate an action potential, a neuron must reach the threshold of excitation.
This means that there is a change in the membrane potential that excites a neuron to fire an impulse. If the threshold of excitation is
reached, then an action potential is triggered thus, a neuron fires an impulse.
