Lecture 20:
The Nervous System/Senses
Covers Chapter 38 & 39
Intro to Nervous System
• Primary Purpose: receive, process and transmit
information
• Messages from the environment and f...
NERVOUS SYSTEM
• 2 parts
– Central Nervous System**
• Brain
• Spinal Cord
– Peripheral Nervous System**
• ALL Neurons/Nerv...
CNS & PNS
3 major types of neurons/nerves
• **Sensory Nerves – carry nerve
impulses TO the CNS
• **Motor Nerves – carry nerve impuls...
stimulus
sensory
neuron spinal
cord
motor
neuron
dorsal root
interneuron
ventral
root
The motor
neuron stimulates
the effe...
Neuron*
• 3 parts of the neuron
• 1.) Cell Body- contains nucleus
• 2.) Dendrites – receives information from
nearby neuro...
Dendrites:
Receive signals
from other neurons
2
Cell body:
Integrates signals;
coordinates the
neuron’s metabolic
activiti...
What is the impulse/signal/message?
• Information is carried in the neuron as an electrical
signal (called an action poten...
How is the message carried
between neurons?*
• Neurons do not actually touch
• The gap between neurons is the synaptic cle...
Neurotransmitters
bind to receptors on the
postsynaptic neuron
dendrite of
postsynaptic
neuron
receptor
neurotransmitter
i...
Types of Neurotransmitters
• Aspartate Serotonin
• Glutamate Endorphins
• GABA Cholyecystokinin
• Glycine Vasopressin
• Ac...
RE-UPTAKE
• After crossing synapse,
neurotransmitters are removed from
synapse by one of two methods:
– NT are reabsorbed ...
Synapse-REUPTAKE
Motor Neurons
• Motor nerves START in CNS
• Motor nerves end in SKELETAL
MUSCLE.
• MN control the actions and movements
we...
Myelin and the Myelin Sheath
• Many (not all) motor neurons have a covering over
their axon called a myelin sheath.
• MS h...
The Sensory Nervous System
• Things that we “sense” in the world is picked
up from sensory receptors, and sent by
sensory ...
Receptors for the sensory
nervous system*
• Receptors are specialized cells that can
register stimuli from outside or insi...
General Senses*
1.) Temperature (thermoreceptors)
2.) Pain (nociceptors)
3.) Touch (mechanoreceptors)
4.) Pressure (mechan...
Pacinian
corpuscle
(vibration,
rapid pressure
changes)
Meissner’s
corpuscle
(light touch,
rapid
movement)
Ruffini corpuscl...
Special Senses*
Receptor location and type:
• 1.) Smell NOSE chemoreceptor
• 2.) Taste TASTE BUDS chemoreceptor
• 3.) Hear...
Sensory neurons of the
special senses
Sense of taste. This map was later proven
wrong. Receptors for each taste are spread
evenly over the tongue.
sclera
choroid
vitreous
humor
retina
fovea
blood
vessels
optic
nerve
blind spot
lens
muscle
aqueous
humor
cornea
lens pupi...
calcium carbonate
stones
semicircular
canals
ampullae
ampulla
gelatinous material
hairs
hair cells
axons from the
auditory...
The Brain
• Housed inside the skull for protection
• Bathed in Cerebrospinal Fluid
(H20, proteins, glucose, WBC’s)
• 100-2...
Parts of the Brain***
• Forebrain:
– Cerebrum: decision-making, emotion, language, interpreting
sensory information
– Thal...
The Human Brain
Fig. 38-12
(a) A lateral section of the human brain (b) A cross-section of the brain
hypothalamus
meninges...
Lecture 20
Lecture 20
Lecture 20
Lecture 20
Lecture 20
Lecture 20
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  • 5 senses SIGHT HEAR TOUCH SMELL TASTE
  • Lecture 20

    1. 1. Lecture 20: The Nervous System/Senses Covers Chapter 38 & 39
    2. 2. Intro to Nervous System • Primary Purpose: receive, process and transmit information • Messages from the environment and from the body itself go to brain and tell it what’s happening. Brain gets info and tells body how to respond. – The cells that carry these “messages” are called NEURONS. – Neurons bundled together are called NERVES.
    3. 3. NERVOUS SYSTEM • 2 parts – Central Nervous System** • Brain • Spinal Cord – Peripheral Nervous System** • ALL Neurons/Nerves outside the CNS
    4. 4. CNS & PNS
    5. 5. 3 major types of neurons/nerves • **Sensory Nerves – carry nerve impulses TO the CNS • **Motor Nerves – carry nerve impulses AWAY from the CNS • **Interneurons - located WITHIN the CNS ONLY- connect sensory and motor neurons
    6. 6. stimulus sensory neuron spinal cord motor neuron dorsal root interneuron ventral root The motor neuron stimulates the effector muscle The effector muscle causes a withdrawal response A painful stimulus activates a pain sensory neuron The signal is transmitted by the pain sensory neuron to the spinal cord The signal is transmitted to an interneuron and then to a motor neuron 4 3 2 1 5 Fig. 38-10
    7. 7. Neuron* • 3 parts of the neuron • 1.) Cell Body- contains nucleus • 2.) Dendrites – receives information from nearby neurons. • 3.) Axon - electrical signals are transmitted to end of neuron (synapse) • Synapse: place where neuron communicates with a muscle fiber, gland or another neuron • Nerve signal sent between neurons takes the form of neurotransmitters.
    8. 8. Dendrites: Receive signals from other neurons 2 Cell body: Integrates signals; coordinates the neuron’s metabolic activities 3 An action potential starts here 4 Axon: Conducts the action potential 5 Dendrites (of other neurons): Receive signals synapse dendrite receptors synaptic terminal 7 Synaptic terminals: Transmit signals to other neurons 6 Synaptic terminals: Transmit signals from other neurons 1 neurotransmitters A Neuron Fig. 38-1
    9. 9. What is the impulse/signal/message? • Information is carried in the neuron as an electrical signal (called an action potential) – When a neuron is stimulated, ions within the neuron (Na+, K+) move in/out and change the electrical charge of the neuron momentarily as the “message” is carried through the neuron – After the action potential passes, neuron’s charge returns to normal
    10. 10. How is the message carried between neurons?* • Neurons do not actually touch • The gap between neurons is the synaptic cleft • At the end of the axon, there is a synaptic terminal. • In the synaptic terminal, vesicles containing chemicals (neurotransmitters) release neurotransmitters from the end of the axon when an action potential reaches the end of the axon. • Neurotransmitters cross synaptic cleft and receptor proteins on the postsynaptic neuron “catch” the neurotransmitters • This triggers an action potential in the postsynaptic neuron • This is how the action potential travels from one neuron to the next
    11. 11. Neurotransmitters bind to receptors on the postsynaptic neuron dendrite of postsynaptic neuron receptor neurotransmitter ions 4 synaptic vesicle synaptic cleft The positive charge of the action potential causes the synaptic vesicles to release neurotransmitters An action potential is initiated The action potential reaches the synaptic terminal of the presynaptic neuron 1 2 3 Neurotransmitters are taken back into the synaptic terminal, are degraded, or diffuse out of the synaptic cleft 6 synaptic terminal of presynaptic neuron neurotransmitters Neurotransmitter binding causes ion channels to open, and ions flow in or out 5 The Structure and Function of the Synapse Fig. 38-4
    12. 12. Types of Neurotransmitters • Aspartate Serotonin • Glutamate Endorphins • GABA Cholyecystokinin • Glycine Vasopressin • Acetylcholine Somatostatin • Dopamine • Noepinephrine
    13. 13. RE-UPTAKE • After crossing synapse, neurotransmitters are removed from synapse by one of two methods: – NT are reabsorbed by the pre-synaptic neuron to be used again – Or NT are digested by enzymes in the synaptic cleft
    14. 14. Synapse-REUPTAKE
    15. 15. Motor Neurons • Motor nerves START in CNS • Motor nerves end in SKELETAL MUSCLE. • MN control the actions and movements we initiate ourselves as well as reactions to the sensory messages we get from the brain.
    16. 16. Myelin and the Myelin Sheath • Many (not all) motor neurons have a covering over their axon called a myelin sheath. • MS helps action potential (the message) travel faster along the axon to the next neuron. • MS made of schwann cells. • Schwann cells contain lipids, which make the the neuron look white, hence the term “white matter” • Unmyelinated neurons look gray, hence the term “gray matter”.
    17. 17. The Sensory Nervous System • Things that we “sense” in the world is picked up from sensory receptors, and sent by sensory nerves to the CNS. – 1.) General Senses* – 2.) Special Senses*
    18. 18. Receptors for the sensory nervous system* • Receptors are specialized cells that can register stimuli from outside or inside the body and send the message (via action potential) to the CNS – Receptors can be • Thermoreceptors: detect heat/cold • Mechanoreceptors: detect vibration, pressure, motion and gravity • Photoreceptors: detect light • Chemoreceptors: detect odors & tastes • Nociceptors: detect pain
    19. 19. General Senses* 1.) Temperature (thermoreceptors) 2.) Pain (nociceptors) 3.) Touch (mechanoreceptors) 4.) Pressure (mechanoreceptors) ALL OF THE ABOVE RECEPTORS ARE LOCATED IN THE SKIN. 5.) Proprioception- position of your limbs in space. (mechanoreceptors) RECEPTORS LOCATED IN MUSCLES AND JOINTS.*
    20. 20. Pacinian corpuscle (vibration, rapid pressure changes) Meissner’s corpuscle (light touch, rapid movement) Ruffini corpuscle (pressure) epidermis dermis subdermal connective and adipose tissue free nerve ending (hair movement) free nerve ending (touch, heat, cold, pain) Receptors in the Human Skin Fig. 39-3
    21. 21. Special Senses* Receptor location and type: • 1.) Smell NOSE chemoreceptor • 2.) Taste TASTE BUDS chemoreceptor • 3.) Hearing INNER EAR mechanoreceptor • 4.) Vision RETINA photoreceptor • 5.) Equilibrium INNER EAR mechanoreceptor (gravity, motion, acceleration)
    22. 22. Sensory neurons of the special senses
    23. 23. Sense of taste. This map was later proven wrong. Receptors for each taste are spread evenly over the tongue.
    24. 24. sclera choroid vitreous humor retina fovea blood vessels optic nerve blind spot lens muscle aqueous humor cornea lens pupil eyelash iris ligaments rod cone signal-processing neurons ganglion cells light (photoreceptors) membrane discs bearing photopigment molecules ganglion cell axons form the optic nerve (a) Eye anatomy (b) Cells of the retina The Human Eye Fig. 39-9
    25. 25. calcium carbonate stones semicircular canals ampullae ampulla gelatinous material hairs hair cells axons from the auditory nerve cochlea auditory nerve saccule utricle gelatinous matrix hairs hair cells axons from the auditory nerve The Vestibular Apparatus Fig. 39-6
    26. 26. The Brain • Housed inside the skull for protection • Bathed in Cerebrospinal Fluid (H20, proteins, glucose, WBC’s) • 100-200 BILLION NEURONS • 100 TRILLION GLIAL CELLS • *Glial Cells: Supportive cells that hold neurons in place* – Supply nutrients and O2 to neurons* – Insulate one neuron from another* – Destroy bacteria and remove dead neurons*
    27. 27. Parts of the Brain*** • Forebrain: – Cerebrum: decision-making, emotion, language, interpreting sensory information – Thalamus: pain, pressure, temperature – Hypothalamus: sex, hunger, thirst, body temp • Midbrain: relay center. Coordinates information sent from hindbrain to forebrain • Hindbrain: – Cerebellum: balance, coordination, movement – Medulla & Pons: swallowing, breathing, heart rate, wakefulness
    28. 28. The Human Brain Fig. 38-12 (a) A lateral section of the human brain (b) A cross-section of the brain hypothalamus meninges skull corpus callosum thalamus cerebellum pons medulla spinal cord cerebral cortex (gray matter) myelinated axons (white matter) basal ganglia hypothalamus hippocampus thalamus corpus callosum substantia nigra MIDBRAIN HINDBRAIN FOREBRAIN (within dashed blue line) cerebral cortex pituitary gland

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