Transcript Nervous System

By: Allie Dunn & Sarah Leitnaker
Evolution of Nervous
system
Hydra (Cndarian)- have one or more
nerve net, made up of neurons.
 Flatworm (planarians)- have ladder like
nervous system

 with two nerve cords that run the length of
the body.
 Connected by transverse nerves
 Cephalization
 Ganglion- a cluster of neurons
Hydra and Flatworm
Evolution of Nervous
system

Earthworms (annelids)
(Also molluscs and arthropods/insects)
 True nervous systems
 A brain, well developed sense organs,
multiple ganglia, and increased number of
neurons.
Evolution of Nervous
system

Humans (vertebrates) Central nervous system with
brain and spinal cord
 With ascending
and descending tracts.
 Peripheral nervous systems
Neurons
Cell body, dendrite, and axon
 Bundled axons form nerves and are
sometimes covered by myelin sheath
 Spiral neuroglia form myelin sheath
membrane.

Types of Neurons

Motor (efferent):
 Nerve impulses for CNS to muscles
 Shape- have many dendrites and a single
axon (multipolar).

Sensory (afferent):
 Takes impulses from sensory receptors to CNS
 Cell body divides into two directions, periphery CNS
(unipolar).

Interneurons:
 Only CNS
 Typical multipolar
Transmission of nerve
impulses
At resting potential the axon has
negative voltage
 Action potential gated channels allow
positive sodium ions to move freely into
axon, voltage becomes positive.
 Myelinated axons: action potential
concentrated at the nodes.

 *refractory period
Synapse
Gap in between neurons (synaptic cleft)
 Neurotransmitter carry impulses across
synaptic cleft. They are released when
calcium gates are open.
 The neurotransmitters bind with the
receptors.
 Neuromodulators block the
neurotransmitter or modifies its
response.

Intermission
Brain and Spinal Cord
Protected by bone i.e. skull and
vertebrae
 Wrapped in meninges, three protective
membranes.
 Spaces in between are filled
cerebrospinal fluid

Spinal Cord
Bundle of nerve tissue from brain to
below rib cage.
 Reflex action center and
communication.

Brain
Four chambers called ventricles
 Cerebrum is the largest portion in
humans. Communicates and
coordinates activities in the brain.

 Divided into lobes.

Diencephalon
 Hypothalamus regulates hunger sleep and
temperature. And controls the pituitary
gland.
 Thalamus receives sensory input.
Brain
Limbic system: blends emotions and
mental functions.
 Two different parts:

 Hyppocampus: awareness of past
experiences
 Amygdala: emotional
overtones on these
experiences
Peripheral Nervous
System
Outside central nervous systems with
nerves.
 Cranial nerves and spinal nerves and be
sensory or motor.
 Somatic system: serves the skin, joint,
and skeletal muscles.

 Reflex arc: sensory receptors generate
nerve impulses. Info is integrated. Impulses
travel along motor axons to an effector
which brings about a response.
Autonomic System
Regulates cardiac and smooth muscles.
 Involuntary
 Use two neurons and one ganglion for
each impulse.

 Sympathetic division for emergency
situations.
 Parasympathetic division for relaxed state.
•Degenerative disease process that affects the basel
ganglia of the brain
•Caused by a deficiency of the neurotransmitter and
aging
•Effects are a tremor, rigidity, and difficulty with
spontaneous movements.
• Also expressionless face, monotone voice and a
shuffling walk.
•A loss or deficiency of motor control
•Caused by injury to the brain before, during or after birth.
•Can also be caused by hypoxia, jaundice, and infection.
•Effects are involuntary spasms and lack of balance.
•Intelligence, posture and speech are frequently
impaired.
•May also be associated with visual impairment,
reduced hearing and behavioral problems
•May have fixed abnormalities
•Associated with a deficiency of ACh.
•Form of dementia that gets worse overtime.
•Affects memory, thinking and behavior.
• Causes abnormal clumps (amyloid plaques) and tangled bundles
of fibers (neurofibrillary tangles).
•There is no cure
•Three different stages:
•Mild
•Moderate
•Severe