Dr/Nahla Yacout2015/2016

Physiology232 BMS

Is the part of the nervous system that consists of the nerves outside the brain & spinal cords

It’s main function: is to connect CNS to the limbs & organs & so acts for communication between the brain & the extremeties

Anatomical classification

Cranial nerves Spinal nerves

They are nerves that emerge directly from the brain & the brainstem reaching head & neck

They are nerves that connect the spinal cord to other parts of the body

Are cluster of neurons that transmit sensory signals

Sympathetic Parasympathetic Are the ganglia of Are the ganglia of

sympathetic nervous system parasympathetic NS They deliver information to the body Are small terminal

about stress & danger (Fight & Flight) ganglia lying near

the organs they innervate

Synaptic cleft:

Is a small gap at the end of a neuron that allows information to pass from one neuron to the next

Pre-ganglionic neuron: Neuron lying before the ganglia

Post-ganglionic neuron Neurons lying after the ganglia

Ach is a neurotransmitter which is released at preganglionic neurons in both sympathetic & parasympathetic stimulation & released at postganglionic neurons in parasympathetic stimulation only

1.Muscarinic (On all organs with parasympathetic nerves)

M1 M2 M3

Actions Increases secretion from salivary glands & stomach

Reduces heart rate & force of contraction

Bronchoconstriction

Agonists Muscarine - ACh

Muscarine - ACh

ACh

Antagonists Atropine Atropine Atropine

2. Nicotinic (In ganglia of both sympathetic & parasympathetic)

Are stimulated by Nicotine & Ach

Noradrenaline is a neurotransmitter of most sympathetic postganglionic neurons & is present also in adrenal medulla

Actions Vasoconstriction Increase in the heart rate Elevation in blood pressure Pupil dilatation Decreases peristalsis in GIT Decreases the contraction of urinary bladder & rectum

Alpha 1 ---- In GIT & urinary bladder Alpha 2 ---- In parts of GIT Beta 1 ---- In the heart Beta 2 ---- In the bronchioles of the lung

Sympathetic Parasympathetic

Stress, Fight & Flight response Rest & digest response

There are two kinds of neurons involved in the transmission of any signal through this system: Pre & Postganglionic neuronsPreganglionic fibers: ShortPostganglionic fibers: Long

Two kinds of neurons involved in the transmission of any signal through this system: Pre & Postganglionic neuronsPreganglionic fibers: LongPostganglionic fibers: Short

Pre-ganglionic neurons release acetylcholine which activates nicotinic acetylcholine (Ach) receptors on postganglionic neurons ---- in response to this stimulus post-ganglionic neurons will release norepinephrine which activates adrenergic receptors on the target tissues

Parasympathetic system uses Acetylcholine as it’s neurotransmitter. Preganglionic neurons release Ach which acts on nicotinic receptors of postganglionic neurons ---- in response postganglionic neurons will release Ach to stimulate the muscarinic receptors of the target organ

Sympathetic Parasympathetic

Rate & force increase

Heart Rate & force decrease

Bronchial muscles relaxed – widening of bronchioles (Allowing more O2 & CO2 exchange)

Lungs Bronchial muscles contracted

Pupil dilatation (Allowing more light)

Eye Pupil constriction

Sympathetic Parasympathetic

Motility is reduced Intestine Digestion is increased

Sphincter closes Urinary bladder Sphincter relaxes

Urine secretion is decreased

Kidneys Urine secretion is increased

Nervous system: Central

Peripheral Neuron: Is the basic unit of nervous system Neurons consist of: Dendrites, Soma, Axon, Presynaptic

terminals Functional classification of neurons: Sensory, Motor &

Interneurons Brain consists of 3 parts: Forebrain (Cerebrum, Thalamus,

Hypothalamus), Midbrain (Tectum & Tagmentum) & Hindbrain (Cerebellum, Pons, Medulla oblongata)

Spinal cord: is the main pathway for information connecting the brain & peripheral nervous system

It consists of 31 nerve segments which are arranged from above as 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, & 1 coccygeal

Peripheral nervous system : is the part of the nervous system that consists of the nerves outside the brain & spinal cords

It consists of 3 types of nerves: Cranial, Spinal & Autonomic nerves

Autonomic ganglia: are cluster of neurons that transmit sensory signals

Acetyl choline (Ach): is a neurotransmitter which is released at preganglionic neurons in both sympathetic & parasympathetic stimulation & released at postganglionic neurons in parasympathetic stimulation only

It’s receptors: Muscarinic – Nicotinic Noradrenaline (NA): is the neurotransmitter of most

sympathetic postganglionic neurons It’s receptors: Alpha1, Alpha2, Beta1 & Beta2