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CONTROL

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Preganglionic neurons in the brainstem and sacral segments of spinal cord Ganglionic neurons in peripheral ganglia located within or near target organs ... – PowerPoint PPT presentation

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Title: CONTROL


1
CONTROL AND COORDINATION
2
NERVOUS SYSTEM
  • The nervous system is composed of
    specialized cells called neuron, which exercise
    control by sending electrical signals called
    nerve impulses. Nerve cells are the structural
    and functional unit of nervous system.

3
STRUCTURE OF NEURON
  • A neuron consists of three prominent parts-
  • 1.Cell body- The cell body of neuron is also
    called cyton or soma. It receives
    nerve impulses from dendrites and transmit them
    to axon.
  • 2.Dendrites- dendrites are the parts of neuron
    where sensation acquired. The information then
    travels as an electric impulse towards the cell
    body.

4
  • Axon-It is a single, cylindrical protoplasmic
    nerve fibre. At its terminal axon is highly
    branched. The axon conducts nerve impulses away
    from the cell body.

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ARRANGEMENT OF NEURON
  • The neurons lie end to end in chains to
    transmit nerve impulses in the animal body. The
    neurons are not connected. There occurs a very
    minute gap between terminal portion of axon of
    one neuron and the dendron of other neuron. This
    minute gap is called synapse.
  • Axon terminal expand to form presynaptic
    knob and dendrite forms post synaptic depression.
    In between the two lies a fluid filled space
    called synaptic cleft.

7
  • As the nerve impulses reaches the pre-synaptic
    knob, the synaptic vesicles get stimulated to
    release a chemical called neurotransmitter in the
    synaptic cleft. The neurotransmitter molecules
    diffuse across the gap to come in contact with
    the chemoreceptor site in the nerve impulses
    passes from one neuron to other.

8
REFLEX ACTIONS
  • A Reflex actions may be defined as a
    spontaneous, automatic and mechanical response to
    a stimulus , acting on a specific receptor ,
    without the will of an animal . In certain
    situation , sensation requires immediate response
    as time used for processing may cause harm to the
    body. In such situation reflex action occur.
  • Example-blinking of eyes ,withdraw of hand
    suddenly pinched or touched by a hot object.

9
HUMAN NERVOUS SYSTEM
  • Human nervous system is the most complex.
    It is divided into two main parts-
  • Central nervous system
  • Peripheral nervous system

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11
CENTRAL NERVOUS SYSTEM
  • It is hollow and lies on the mid-dorsal
    part along the main axis of the body. It is
    covered by a part of axial skeleton. The CNS in
    turn consists of two parts-
  • 1. Brain or Encephalon situated in the head.
  • 2. Spinal cord or Myelon located in the neck and
    trunk.

12
BRAIN
  • The brain is the widest and the uppermost part
    of the central nervous system . It is the highest
    coordinating centre in the body. Brain is
    situated in the cranial cavity of the skull. The
    brain is soft, whitish organ. It weighs 1.2 to
    1.4 kg and forms about 98 of the weight of the
    whole nervous system. It has about 100 bilion
    neurons. Brain is surrounded by three membranes
    called meninges which provide protection to it.
    The space between the meninges is filled with the
    cerebro- spinal fluid .

13
  • Brain is divisible into three main region
  • FOREBRAIN- It forms the greater part of the
    brain. It consists of three parts olfactory
    lobes, cerebral hemisphere and diencephalon.
  • i) Olfactory lobes- A pair of widely
    separated club- shaped small structure . Each
    olfactory lobe consist of an anterior olfactory
    bulb and a posterior narrow olfactory stalk.
    These lobes receive impulses from
    olfactoreceptors and relay sense of smell to the
    temporal region of the cerebrum.

14
  • (ii) Cerebral hemisphere- It is the largest part
    of the brain . The two cerebral hemisphere lie
    side by side separated by deep cerebral fissure.
    The cerebral hemisphere divided into four lobes
  • a. Frontal lobe is the region for speech
    ,facial, muscular activities and mental
    activities.
  • b. Temporal lobe is the region for auditory
    reception (hearing ) .
  • c. Occipital lobe is the region for visual
    reception (sight )
  • d. Parietal lobe is the region for touch ,taste
    ,smell, temperature and conscious association.

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  • (iii) Diencephalon-It lies on the side of
    cerebrum It roof is called epithalamus, sides are
    called thalami and its floor is called
    hypothalamus. Diencephalon has a narrow cavity
    called third ventricle.
  • 2. MID BRAIN-It is significantly small region.
    It consists of two fibre tracts called crura
    cerebri and a pair of two swellings called
    superior and infeior colliculi on each side. the
    two superior colliculi have centres for sight
    reflexes and the two inferior colliculi have
    centre for sight reflexes. It controls the
    movement of head, neck, eye muscles changes in
    pupil size as well as shape of eye lens.

17
  • 3. HIND BRAIN- The hind brain consists of three
    parts- cerebellum, pons varolii and medulla
    oblongata. The cerbellum is the second largest
    part of the brain , constituting nearly 12 of
    it. It has two large, lateral cerebellar
    hemispheres and a central vermis. Cerebellum
    maintains the posture, equilibrium and muscles
    tone. Pons varolii controls some aspects of
    respiration. Medulla oblongata is the posterior
    part of the brain. It controls rate of heartbeat,
    breathing movements etc.

18
SPINAL CORD
  • Spinal cord is a cylindrical structure and is
    about 45cm long . It begins in continuation with
    the medulla oblongata of brain extend downward
    up to early part of the lumber region . It then
    extend to the end of vertebral column as fibrous
    connective called filum terminale. Internally the
    spinal cord possess a narrow, fluid filled cavity
    called central canal. Spinal cord is enclosed in
    the vertebral column or backbone which protect
    it. It conducts sensory and motor impulses to and
    from the brain. It act as center for the reflex
    action

19
PERIPHERAL NERVOUS SYSTEM
  • It connects CNS with different part of the
    body . It has two component, voluntary and
    Autonomic nervous system. These are-
  • 1. Voluntary peripheral nervous system is under
    the control of will. It consist of nerves that
    arise directly from CNS connecting different body
    parts for voluntary control of the brain.

20
  • 2. Autonomic nervous system (involuntary
    nervous system), on other hand, is not under the
    control of human will. It developed branches of
    some cranial and some spinal nerves called
    visceral nerves. It is subdivided into two parts
  • (i) sympathetic nervous system
  • (ii) parasympathetic nervous system

21
The Organization of the Sympathetic Division of
the ANS
22
Sympathetic ganglia
  • Sympathetic chain ganglia (paravertebral ganglia)
    preganglionic fibers of the sympathetic NS that
    carry motor impulses to the body wall or thoracic
    cavity synapses in chain ganglia
  • Collateral ganglia (prevertebral ganglia)
    group of second order neurons that innervate
    organs in the abdominopelvic region

23
Sympathetic Pathways
24
Sympathetic Pathways
25
Sympathetic Pathways
26
The Distribution of Sympathetic Innervation
Animation The sympathetic division (see tutorial)
27
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28
Postganglionic fibers
  • Rejoin spinal nerves and reach their destination
    by way of the dorsal and ventral rami
  • Those targeting structures in the thoracic cavity
    form sympathetic nerves
  • Go directly to their destination

29
Abdominopelvic viscera
  • Sympathetic innervation via preganglionic fibers
    that synapse within collateral ganglia
  • Splanchic nerves carry fibers that synapse in
    collatheral ganglia

30
Abdominopelvic viscera
  • Celiac ganglion
  • Innervates stomach, liver, gall bladder,
    pancreas, spleen
  • Superior mesenteric ganglion
  • Innervates small intestine and initial portion of
    large intestine
  • Inferior mesenteric ganglion
  • Innervates kidney, urinary bladder, sex organs,
    and final portion of large intestine

31
Sympathetic activation
  • Sympathetic activation is controlled by
    sypathetic centers in the hypothalamus.
  • In crises, the entire sympathetic division
    responds
  • Sympathetic activation
  • Affects include increased alertness, energy and
    euphoria, increased cardiovascular and
    respiratory activities, elevation in muscle tone,
    mobilization of energy resources

32
Neurotransmitters and sympathetic function
  • Stimulation of sympathetic division has two
    distinct results
  • Release of ACh or NE at specific locations
  • Secretion of E and NE into general circulation
  • Most postganglionic fibers are adrenergic, a few
    are cholinergic or nitroxidergic

33
Sympathetic Variosities
34
Parasympathetic division
  • Preganglionic neurons in the brainstem and sacral
    segments of spinal cord
  • Ganglionic neurons in peripheral ganglia located
    within or near target organs

35
The Organization of the Parasympathetic Division
of the ANS
36
Organization and anatomy of the parasympathetic
division
  • Preganglionic fibers of parasympathetic neurons
    can be found in cranial nerves III, VI, IX, X
  • Sacral neurons form the pelvic nerves
  • Almost 75 of all parasympathetic outflow travels
    along the vagus nerve (cranial nerve X)

37
The Distribution of Parasympathetic Innervation
38
Parasympathetic activation
  • Effects produced by the parasympathetic division
  • relaxation
  • food processing
  • energy absorption

39
Neurotransmitters and parasympathetic functions
  • All parasympathetic fibers release ACh
  • Short-lived response as ACH is broken down by
    AChE and tissue cholinesterase

40
Sympathetic and parasympathetic divisions
  • Sympathetic
  • Widespread influence on visceral and somatic
    structures
  • Parasympathetic
  • Innervates only visceral structures serviced by
    cranial nerves or lying within the abdominopelvic
    cavity
  • Effects produced by the parasympathetic branch
    include increased secretion by digestive glands
  • Dual innervation organs that receive input from
    both systems

41
Anatomy of dual innervation
  • Sympathetic and parasympathetic systems
    intermingle to form autonomic plexuses
  • Cardiac plexus sympathetic and parasympathetic
    fibers bound for the heart and kungs pass through
    the cardiac plexus
  • Pulmonary plexus
  • Esophageal plexus
  • Celiac plexus
  • Inferior mesenteric plexus
  • Hypogastric plexus

42
The Autonomic Plexuses
43
Comparison of the two divisions
  • Important physiological and functional
    differences exist

44
Summary The Anatomical Differences between the
Sympathetic and Parasympathetic Divisions
45
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46
A Comparison of Somatic and Autonomic Function
47
Higher levels of autonomic control
  • Activity in the ANS is controlled by centers in
    the brainstem that deal with visceral functioning

48
Levels of Autonomic Control
Example of higher-level of autonomic function
would be increased heart rate when you see a
person that you dislike.
49
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50
Higher order functions
  • Are performed by the cerebral cortex and involve
    complex interactions
  • Involve conscious and unconscious information
    processing
  • Are subject to modification and adjustment over
    time

51
Memory
  • Short term or long term
  • Memory consolidation is moving from short term to
    long term
  • Hippocampus is essential for memory consolidation
  • Mechanisms involved in memory formation and
    storage are
  • Increased release of neurotransmitter
  • Formation of additional synaptic connection
  • Formation of memory engrams (single circuit that
    correspond to single memory)
  • Amnesia is the loss of memory due to disease or
    trauma

52
Memory
  • Memory that can be voluntarily retrieved and
    verbally expressed are called declarative
    memories
  • Conversion of a short term memory to a long term
    memory is called memory consolidation

53
Memory Storage
54
Consciousness
  • Deep sleep, the body relaxes and cerebral cortex
    activity is low
  • The reticular activating system (RAS) is
    important to arousal and maintenance of
    consciousness
  • RAS is located in the mesencephalon

55
The Reticular Activating System
56
Age-related changes
  • Reduction in brain size and weight
  • Reduction in the number of neurons
  • Decrease in blood flow to the brain
  • Changes in synaptic organization of the brain
  • Intracellular and extracellular changes in CNS
    neurons

57
You should now be familiar with
  • The organization of the autonomic nervous system.
  • The structures and functions of the sympathetic
    and parasympathetic divisions of the ANS.
  • The mechanisms of neurotransmitter release in the
    sympathetic and parasympathetic divisions.
  • The effects of sympathetic and parasympathetic
    neurotransmitters on target organs and tissues.
  • The hierarchy of interacting levels of control in
    the ANS.
  • How memories are created, stored and recalled.
  • The effects of aging on the nervous system.
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