Case 1 – organisation and
function of CNS
And peripheral nervous system
What is the general anatomy and function of the CNS
(and PNS)
- Anatomical classification of the brain is done using ‘the lobe division of the brain’
A fifth lobe, known as
the insula, is located
deep within the parietal
and temporal lobes and
is not apparent as a
separate structure on
the outer surface of the
cerebral hemispheres.
- Meninges= membranes in between skull and brain tissue
1. Dura mater
2 layers tough and inflexible connective tissue
Surrounds brain and spinal cord
2. Arachnoid membrane
Interposed layer – spider web shape
Around brain and spinal cord not in sulci (hersengroeve) except for longitudinal
fissure
3. Subarachnoid space
4. Pia mater
Thin layer with blood vessels
Adheres to surface of brain into fissures
,- Ventricular system= a set of 4 ventricles (cavities in the brain) that are responsible for the
production transport and removal of cerebrospinal fluid
Choroid plexus (plexus= branching network of vessels or nerves) in each of the
ventricles produces most of the CSF
CSF provides mechanical (cushion) and immunological protection
CSF has an important function in filling the subarachnoid space
- Brainstem:
Consists of 4 part: the diencephalon, mesencephalon, pons and medulla oblongata
Medulla oblongata crossover for many afferent and efferent nerves and
is the seat for several nerves that go to from the abdomen, chest and head
Pons (top of stem) bridge between brainstem and midbrain and origin of
many facial nerves (mesencephalon)
Serves as a connection between the cerebral hemispheres cerebellum and spinal
cord
Responsible for basic vital function (breathing, heartbeat, BP, control of
consciousness, sleep, etc.)
- Thalamus and Hypothalamus
Located deep in the brain just above the brainstem
Thalamus consists of 2 oval masses containing nerve
cell bodies (one in each hemisphere) connected by a
bridge
Thalamus sorts info from the senses and
relays that info to the cerebral cortex
Pain, temp and pressure sensations are also
processed by the thalamus
Hypothalamus is the main point of interaction for the
body’s 2 physical control systems nervous system and endocrine system
It recognises changes in the body and stimulates organs and glands to
release hormones
, Translates emotion into physical response
Hypothalamus contains nerves that monitor body temp at the surface of
the skin – and internal temp via nerves in the brain itself
Hypothalamus also controls food and water intake
Hypothalamus might play a role in the induction of sleep
- Pituitary and pineal glands
Function in close association with the hypothalamus
The pituitary glands responds to signals from the hypothalamus by producing an
array of hormones
Many of which regulate the activities of other glands: thyroid-stimulating
hormone, adrenocorticotropic hormone (which stimulates an outpouring of
epinephrine in response to stress), prolactin (involved in the production of
milk), and the sex hormones follicle-stimulating hormone and luteinizing
hormone, which promote the development of eggs and sperm and regulate
the timing of ovulation
The pituitary gland also produces several hormones with more general
effects: human growth hormone, melanocyte-stimulating hormone (which
plays a role in the pigmentation of skin), and dopamine, which inhibits the
release of prolactin but is better known as a neurotransmitter
The pineal gland produces melatonin, the hormone associated sleep
The secretion of melatonin varies significantly over a 24-hour cycle, from
low levels during the day to a peak at night
The pineal gland has been called a "third eye" because it is controlled by
neurons sensitive to light, which originate in the retina of each eye and end
in the hypothalamus.
- The cerebellum – small brain
The cerebellum is positioned at the back of the head, partly tucked under the
cerebral hemispheres
In humans, with our almost unlimited repertoire of movement, the cerebellum is
accordingly large – second largest brain area after cerebral cortex (many sulci and
gyri)
Required to maintain balance and posture and to carry out coordinated movement
Cerebellum compares the impulses going to and from the muscles to make
coordinated movements
Impulse from motor area cerebral cortex cerebellum spinal cord
designated muscle groups
Impulse from muscles cerebellum thalamus muscle groups
Each hemisphere of the cerebellum processes impulses from the same side of the
body and the contralateral side of the cerebral cortex
Nerve impulses concerned with movement of the left arm originate in the
right cerebral hemisphere, and information about the orientation, speed,
and force of the movement is fed back to the right cerebral hemisphere,
through the left half of the cerebellum.
- Reticular Network
Reticular activation system responsible for maintaining consciousness and focussing
thoughts – the cell bodies are located in the brainstem
, Nerve fibers from the cerebellum and some neurons in the thalamus,
together with others from various sensory systems of the brain, make up
the reticular activating system
At the midline of the brainstem are the raphe nuclei, whose axons extend
down into the spinal cord and up to the cerebral cortex – enables many
areas of the nervous system to be in contact with each other
simultaneously
The reticular formation plays a role in ‘unconscious movement’
It is also involved in transmitting or inhibiting sensations of pain, temperature, and
touch
The reticular activating system appears to work as a filter for the countless stimuli
that can act on the nervous system both from within and from outside the body
- Limbic system
The limbic system is responsible for most of the basic drives and emotions and the
associated involuntary behaviour that are important for an animal's survival: pain
and pleasure, fear, anger, sexual feelings, and even docility (obedience) and
affection.
Consists of a t least 12 parts that can be divided into cortical areas, subcortical areas
and diencephalic structures
Diencephalic structures like the thalamus and hypothalamus
Subcortical areas including the amygdala that receives input from both the
olfactory system and the cerebral cortex.
Cortical areas like the hippocampus
The limbic system is an assembly of linked structures that form a loose circuit
throughout the brain
Many other vertebrates have a similar structure; in reptiles, it is known as
the rhinencephalon, or "smell-brain," because it reacts primarily to signals
of odour. In humans, of course, the stimuli that can affect the emotional
brain are just about limitless in their variety.
As with the rhinencephalon, the sense of smell is a powerful factor. Nerves
from the olfactory bulb, by which all odour is perceived, track directly into
the limbic system at several points and are then connected through it to
other parts of the brain; hence the ability of pheromones, and perhaps of
other odours as well, to influence behaviour in quite complex ways without
necessarily reaching our conscious awareness.
- Cerebral cortex
The largest and most striking part of the human brain last to evolve
many sulci, gyri and fissures to increase surface area
These gyri, sulci and fissures are not randomly dispersed – highly ordered
structure (unknown)
