NERVOUS SYSTEM

T. Naga Varalakshmi,

Assistant Professor,Dept of

PharmacologyNirmala College

of Pharmacy, Guntur

1. Sensory input – gathering information· To monitor changes occurring inside

and outside the body (changes = stimuli)

2. Integration –· to process and interpret sensory input

and decide if action is needed.3. Motor output

· A response to integrated stimuli· The response activates muscles or

glands

Functions of the Nervous System

Classification of Nervous System

Neuron• Cells of the nervous system are called nerve cells or neurons which carry "messages" through an electrochemical process called Action Potential. • The human brain has about 100 billion neuron.• Dendrites receive signals.• The cell body integrates signals.• The axon transmits action potential. The myelin sheath makes the signal travel faster.• Synaptic terminals transmit signals.

Basic nerve cell and Synapse

T.S. of Nerve

Action Potential

Some Neurotransmitters

Neurotransmitter Location Some Functions

Acetylcholine Neuron-to-muscle synapse Activates muscles

Dopamine Mid-brain Control of movement

Epinephrine Sympathetic system Stress response

Serotonin Midbrain, pons, medulla Mood, sleep

Endorphins Brain, spine Mood, pain reduction

Nitric Oxide Brain Memory storage

Supporting Cells (Neuroglia or Glia)

CENTRAL NERVOUS SYSTEM

Parts of Brain

Meninges of brain

Divisions of the Brain

Major Division Subdivision Structures

Prosencephalon (Forebrain)

Telencephalon Neocortex; Basal Ganglia; Amygdala; Hippocampus; Lateral Ventricles

Diencephalon Thalamus; Hypothalamus; Epithalamus; Third Ventricle

Mesencephalon (Midbrain) Mesencephalon Tectum; Tegmentum; Cerebral Aqueduct

Rhombencephalon (Hindbrain)

Metencephalon Cerebellum; Pons; Fourth Ventricle

Myelencephalon Medulla Oblongata; Fourth Ventricle

Telencephalon

Diencephalon

Mesencephalon (Midbrain) Metencephalon

Myelencephalon

The subdivisions of the brain

CEREBRUM

The cerebrum is the largest portion of the brain, consists of 2 Cerebral hemispheres, which are connected by Corpus Callosum. The surface of the brain is marked by Gyri, Sulci, and Fissures. A thin layer of Gray matter, lines outside of the Cerebral cortex and contains 75% of the cell bodies in the nervous system. Beneath the cortex is the White matter made up of myelinated nerve fibers connecting the cell bodies of the cortex with the rest of the nervous system.

Lobes of the Brain

Functional Areas of the Cerebral Cortex

Thalamus and Hypothalamus

Basal Ganglia

Brain Function: Cerebral Lateralization

Primary Motor Cortex

Primary Somatosensory

Cortex

Association areas of brain

Brain StemIt consists of the

Midbrain, Pons Medulla oblongata

MIDBRAIN: Located between Diencephalon and Pons, Contains bundles of myelinated nerve fibers that

convey impulses to and from higher parts of the brain, and masses of gray matter that serve as reflex centers.

It is the main centre for auditory and visual reflexes.

PONS Lying between the midbrain and medulla oblongata, transmits impulses between the brain and spinal cord. It contains centers that regulate the rate and depth of breathing.MEDULLA OBLONGATA It transmits all ascending and descending impulses between the brain and spinal cord. It contain

Cardiac center that controls heart rate, Vasomotor center for blood pressure control, Respiratory center that works along with the

Pons, to control the rate and depth of breathing.

Brain Stem: Midbrain, Pons & Medulla

Major Functions

1. Sensory perception2. Voluntary control of movement3. Language4. Personality traits5. Sophisticated mental events, such as thinking memory, decision making, creativity, and self-consciousness

1. Inhibition of muscle tone2. Coordination of slow, sustained movements3. Suppression of useless patterns of movements1. Relay station for all synaptic input2. Crude awareness of sensation3. Some degree of consciousness4. Role in motor control

1. Regulation of many homeostatic functions, such as temperature control, thirst, urine output, and food intake2. Important link between nervous and endocrine systems3. Extensive involvement with emotion and basic behavioral patterns1. Maintenance of balance2. Enhancement of muscle tone3. Coordination and planning of skilled voluntary muscle activity

1. Origin of majority of peripheral cranial nerves2. Cardiovascular, respiratory, and digestive control centers3. Regulation of muscle reflexes involved with equilibrium and posture4. Reception and integration of all synaptic input from spinal cord; arousal and activation of cerebral cortex5. Role in sleep-wake cycle

Cerebral cortex

Basal nuclei

Thalamus

Hypothalamus

Cerebellum

Brain stem(midbrain, pons,and medulla)

Cerebellum The cerebellum is made up of two hemispheres connected by a vermis. A thin layer of gray matter called the cerebellar cortex lies outside a core of white matter. The cerebellum communicates with other parts of the CNS through cerebellar peduncles. Functions –

integrate sensory information about the position of body parts

Coordinates skeletal muscle activity Maintains posture.

SPINAL CORD

The spinal cord consists of 31segments, each of which gives rise to a pair of spinal nerves. Two deep longitudinal grooves (anterior median fissure and posterior median sulcus) divide the cord into right and left halves. White matter, made up of bundles of myelinated nerve fibers (nerve tracts), surrounds a butterfly-shaped core of gray matter . A central canal contains cerebrospinal fluid.

39

REFLEX ARC

To transmit impulses to and from the brain, Carrying sensory information to the brain are called ascending tracts; Descending tracts carry motor information from the brain.

Functions of the Spinal Cord

Peripheral Nervous System

PNS consists of

Cranial nerves

Spinal nerves

They arise from the CNS

and travel throughout the

body. PNS -- Somatic (voluntary

activities), Autonomic

(involuntary activities).

Cranial Nerves

Autonomic Nervous System

Parasympathetic Sympathetic Nervous System

Sympathetic system ready the body for

an emergency

Para Sympathetic system restores the

body for Homeostasis

Disorders of Nervous System1.Alzheimer’s Disease 2. Parkinson’s Disease3. Dementia4. Cerebral Hypoxia5. Multiple sclerosis6. Phenylketonuria7. Encephalitis8. Neuritis9. Spina bifida

10. Depression11.Psychosis12. Mania 13. Tumours14. Neuropathy15. Meningitis16. Stroke17.Hydrocephal

us etc