The document provides information on the central nervous system including: 1) It describes the basic components and function of neurons including synapses and neurotransmitters. 2) It discusses reflexes and the reflex arc as the simplest neural pathway. 3) It provides details on the main parts of the brain - cerebrum, cerebellum, and brainstem - and their functions.

1. DR MUSADDIQ KHAN DURRANI
M B B S , M C P S ®
Central Nervous System

4.  A stimulus is a change in the environment with
sufficient strength to initiate a response.
 Synapse - Junction where one neuron interacts with
another neuron or effector organ.
 Neurotransmitters – Chemicals in the junction
which allow impulses to be started in the second
neuron

5.  Reflexes :
Involuntary reactions in response to a stimulus
that’s applied to a sensory organ and transmitted to the motor
organ
 Reflex Arc – simplest neural pathway by which a reflex
occurs – basic functional unit/smallest and simplest pathway
capable of receiving a stimulus and yielding a response –
consists of 5 components
a) Sensory receptor – initial stimulation happens here →
b) Sensory neuron – transports message →
c) Interneuron – located in the CNS (usually the spinal cord)
not part of all reflexes
d) Motor neuron – transports response message →
e) Effector organ

7.  Brain one of largest organs in body:
 Average 1,600 g (3.5 lbs)
 Size is proportional to body size not intelligence
 consumes 20% of our oxygen need at rest
 >4 min w/o oxygen leads to permanent damage
besides O2 must get continuous supply of glucose
very little in reserve
 Decrease in glucose:
1. Dizziness
2. convulsions
3. unconsciousness

8.  The brain is housed inside the bony covering called the
cranium(Skull)
 Between the skull and brain is the meninges, which
consist of three layers of tissue that cover and protect the
brain and spinal cord. From the outermost layer inward
they are:
 Dura mater
(Sub Dural Space)
 Arachnoid mater
 (Sub Arachnoid Space , Contains CSF)
 Pia mater.

13.  The brain has three main parts: the cerebrum, cerebellum and
brainstem.
 Cerebrum: is the largest part of the brain and is composed of
right and left hemispheres. It performs higher functions like
interpreting touch, vision and hearing, as well as speech,
reasoning, emotions, learning, and fine control of movement.
 Cerebellum: is located under the cerebrum. Its function is to
coordinate muscle movements, maintain posture, and
balance.
 Brainstem: acts as a relay center connecting the cerebrum
and cerebellum to the spinal cord.
It performs many automatic functions such as breathing, heart
rate, body temperature, wake and sleep cycles, digestion,
sneezing, coughing, vomiting, and swallowing.

14.  Brainstem
1. Midbrain
2. Pons
3. Medulla oblongata

18. The Cerebrum
 The cerebrum (front of brain) comprises gray matter (the
cerebral cortex) and white matter at its center.
 The cerebral cortex is divided into two halves, or hemispheres.
 It is covered with ridges (gyri) and folds (sulci).
 The two halves join at a large, deep sulcus( medial
longitudinal fissure) that runs from the front of the head to
the back.
 The right hemisphere controls the left side of the body, and
the left half controls the right side of the body.
 The two halves communicate with one another through a
large, C-shaped structure of white matter and nerve pathways
called the corpus callosum. The corpus callosum is in the
center of the cerebrum.

19.  In general, the left hemisphere controls speech,
comprehension, arithmetic, and writing.
 The right hemisphere controls creativity, spatial
ability, artistic, and musical skills.
 The left hemisphere is dominant in hand use and
language in about 92% of people.

20.  Cerebral cortex is classified into four lobes

22. Frontal lobe
 located beneath the frontal bone
 most anterior region of the cerebrum
 separated from the parietal lobe posteriorly by
the central sulcus and from the temporal lobe
inferoposteriorly by the lateral sulcus.
 Personality, behavior, emotions
 Judgment, planning, problem solving
 Speech: speaking and writing (Broca’s area)
 Body movement (motor strip)
 Intelligence, concentration, self awareness

23. Parietal Lobe
 found below the parietal bone
 between the frontal lobe anteriorly and the occipital
lobe posteriorly, from which it is separated by the
central sulcus and parieto-occipital sulcus
 language and calculation on the dominant
hemisphere side, and visuospatial functions
 Interprets language, words Wernickes Area
 Sense of touch, pain, temperature (sensory strip)
 Interprets signals from vision, hearing, motor, sensory and memory
 Spatial and visual perception

24. Temporal Lobe
 Beneath Temporal Bone
 primary auditory cortex.’
 Understanding language
 Memory
 Hearing
 Sequencing and organization

25. Occipital Lobe
 The most posterior part of the cerebrum
 primary visual cortex

27.  Aphasia is a disturbance of language affecting speech production,
comprehension, reading or writing, due to brain injury – most
commonly from stroke or trauma. The type of aphasia depends on
the brain area damaged.
 Broca’s area: If this area is damaged, one may have difficulty
moving the tongue or facial muscles to produce the sounds of
speech. The person can still read and understand spoken language
but has difficulty in speaking and writing (i.e. forming letters and
words, doesn't write within lines) – called Broca's aphasia.
 Wernicke's area: Damage to this area causes Wernicke's aphasia.
The individual may speak in long sentences that have no meaning,
add unnecessary words, and even create new words. They can make
speech sounds, however they have difficulty understanding speech
and are therefore unaware of their mistakes.

30. Cerebellum
 Cerebellum, which stands for “little brain”, is a structure of the central
nervous system. It has an important role in motor control, with
cerebellar dysfunction often presenting with motor signs.
 Fine movement coordination
 Balance and equilibrium
 Muscle tone
 Sense of body position
 The cerebellum processes information from the brain and PNS for
balance and body control.

31.  GAIT
 COORDINATION
 FINGER NOSE TEST

32. Deep Structures
 Hypothalamus: is located in the floor of the third ventricle and is
the master control of the autonomic system. It plays a role in
controlling behaviors such as hunger, thirst, sleep, and sexual
response. It also regulates body temperature, blood pressure,
emotions, and secretion of hormones.
 Pituitary gland: The pituitary gland is connected to the
hypothalamus of the brain by the pituitary stalk. Known as the
“master gland,” it controls other endocrine glands in the body. It
secretes hormones that control sexual development, promote bone
and muscle growth, and respond to stress.
 Pineal gland: is located behind the third ventricle. It helps
regulate the body’s internal clock and circadian rhythms by
secreting melatonin. It has some role in sexual development.
 Thalamus: serves as a relay station for almost all information that
comes and goes to the cortex. It plays a role in pain sensation,
attention, alertness and memory.

33. CIRCLE OF WILLIS
 The circle of Willis is a ring of vessels connecting the
anterior and posterior circulations of the brain.
 provide collateral blood flow between the anterior
and posterior circulations of the brain, protecting
against ischemia in the event of vessel disease or
damage in one or more areas.

34.  Two arteries, called the carotid arteries, supply blood to the brain.
They run along either side of the neck and lead directly to the circle
of Willis.
 Each carotid artery branches into an internal and external carotid
artery. The internal carotid artery then branches into the cerebral
arteries. This structure allows all of the blood from the two internal
carotid arteries to pass through the circle of Willis.
 The structure of the circle of Willis includes:
 left and right internal carotid arteries
 left and right anterior cerebral arteries
 left and right posterior cerebral arteries
 left and right posterior communicating arteries
 basilar artery
 anterior communicating artery

35. BLOOD SUPPLY OF BRAIN

36. s

38. CVA/Stroke
 A cerebrovascular accident (also known as a stroke)
is defined clinically as “an abrupt loss of focal brain
function lasting more than 24 hours due to either
spontaneous haemorrhage into brain substance or
inadequate blood supply to part of the brain i.e.
ischaemia (thrombosis, embolism)“.

39.  Alzeihmers
 Fits/Seizures
 Tumor
 Trauma

40.  Which lobe of the cerebral cortex is responsible for
generating motor commands?
 temporal
 parietal
 occipital
 frontal

41.  d