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Nervous System.

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Presentation on theme: "Nervous System."— Presentation transcript:

1 Nervous System

2 B. Supporting cells of the CNS
Oligodendrocytes Astrocytes: protoplasmic fibrous Microglia Ependymal cells

3 ① oligodendrocytes One oligodendrocyte may myelinate one axon or several nearby axons

4 ② Astrocytes Protoplasmic astrocyte Fibrous astrocyte

5 ③ Ependymal cells Line the brain ventricles and central canal of the spinal cord Some are ciliated to facilitate the movement of cerebrospinal fluid

6 ④ Microglia Derived from bone marrow, phagocyte in nerve tissue
Involved with inflammation and repair in the CNS

7 Summary 2 Supporting cells in the PNS Myelin sheath neuroglia

8 I. The peripheral nervous system
Nerve fibers Ganglia Nerve ending

9 1. Nerve fibers A peripheral nerve is a bundle of nerve fibers held together by connective tissue

10 Unmyelinated nerve fiber

11 2. Ganglia Ovoid structures containing neuronal cell bodies and glial cells supported by connective tissue The direction of the nerve impulse determines whether sensory or autonomic ganglia.

12 Sensory ganglia: receive afferent impulses that go to the CNS
Cranial ganglia: cranial nerves Spinal ganglia: dorsal root of spinal nerves Autonomic ganglia: Sympathetic: paravertebrate, preveterbrate Parasympathetic: close to organs or in organs

13 3. Nerve ending Sensory nerve ending Motor nerve ending
Free: pain, temperature encapsulate Motor nerve ending Motor end plate Visceral motor Tactile corpuscle: sense of touch Lamellar corpuscle: pressure, vibration Muscle spindle: limbs position

14 Tactile corpuscle Lamellar corpuscle Muscle spindle Motor end plate

15 Autonomic nervous system
The ANS consists of motor neurons that: Innervate smooth and cardiac muscle and glands (most of the effectors are viscera)


17 Three major differences in the ANS and SNS
Effectors Efferent pathways Target organ responses

18 Effectors The effectors of the SNS are skeletal muscles
The effectors of the ANS are cardiac muscle, smooth muscle, and glands

19 Efferent Pathways Myelinated axons of the somatic motor neurons extend from the CNS to the effector (lacks ganglia) Pathways in the ANS are a two-neuron chain The preganglionic (first) neuron has a lightly myelinated axon. The ganglionic (second) unmyelinated neuron extends to an effector organ via the postganglionic axon

20 Neurotransmitter Effects
All somatic motor neurons release Acetylcholine at their synapses, Ach always has an excitatory effect In the ANS: Preganglionic fibers release ACh Postganglionic fibers release norepinephrine (most s.) or ACh (p.) and the effect is either stimulatory or inhibitory


22 The nuclei of the Sym. are located in the thoracic and lumbar segments of the spinal cord.
The 2nd neuron is located in sensory ganglia. The nuclei of the Para. are located in the medulla and midbrain and in the sacral portion of the spinal cord. The 2nd neuron is in ganglia located near or within the effector organs

23 II. The central nervous system
Cerebrum Cerebellum Spinal cord CNS has almost no connective tissue, A relatively soft gel-like tissue.

24 White matter Gray matter
Myelinated nervous fibers and oligodendrocytes Gray matter Neuronal cell bodies dendrites Initial segment Glial cells

25 1. Cerebrum The gray matter forms cortex, the white matter forms medulla. Cerebral cortex has six layers of cells

26 Sensory inputs first activate neurons in layer 4, which propagate the excitement up to layer 2,3, and down to layer 5,6

27 2. Cerebellar cortex has 3 layers
Out molecular layer Purkinje cells layer Inner granular layer Purkinje cells are the efferent neurons Mossy and climbing fibers are afferent fibers


29 3. Spinal cord DH: sensory fibers form dorsal root VH: motor neurons


31 4. Connective tissue of the CNS
Meninges Connective tissue encase the skull and the vertebral column Dura mater Arachnoid Pia mater The region between the arachnoid and pia mater is filled with CSF

32 5. Blood-brain barrier (BBB)
Prevents the passage of some substances, such as chemical and bacterial toxin matter, from the blood to nerve tissue

33 Response of neurons to injury

34 Summary The PNS Nerve fibers, ganglia, nerve ending
Autonomic nerve system The CNS Spinal cord Cerebrum Cerebellum Meninges

35 Questions List differences between the Central and Peripheral nervous systems. List difference between the somatic and autonomic nervous systems 

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