an introduction to the nervous system organization and nerve cells
TRANSCRIPT
An Introduction to the An Introduction to the Nervous SystemNervous System
Organization and nerve cellsOrganization and nerve cells
What is the nervous What is the nervous system?system?
A network of specialized cells A network of specialized cells throughout your body.throughout your body.
Carry electrochemical messages from Carry electrochemical messages from one part of the body to another.one part of the body to another.
Interacts with the endocrine system Interacts with the endocrine system to maintain homeostasis.to maintain homeostasis.
Nervous system works much faster Nervous system works much faster than the endocrine system than the endocrine system (electrochemical messages relayed (electrochemical messages relayed by the brain versus chemical by the brain versus chemical messages carried in the blood.messages carried in the blood.
Divisions of the Nervous Divisions of the Nervous SystemSystem
Central Nervous System (CNS): Central Nervous System (CNS): consists of the brain and spinal cord.consists of the brain and spinal cord. CNS is the control center for the body, CNS is the control center for the body,
actions (and messages) must pass actions (and messages) must pass through the CNS before being performed.through the CNS before being performed.
Peripheral Nervous System (PNS): all Peripheral Nervous System (PNS): all other parts of the nervous system. other parts of the nervous system. Relays info between the CNS and Relays info between the CNS and other parts of the body.other parts of the body.
Divisions of the Nervous Divisions of the Nervous SystemSystem
The PNS can be divided further into the somatic The PNS can be divided further into the somatic nervous system and the autonomic nervous nervous system and the autonomic nervous system. system.
The somatic nervous system controls voluntary The somatic nervous system controls voluntary movements of the body involving the skeletal movements of the body involving the skeletal muscles, bones and skin. It includes motor and muscles, bones and skin. It includes motor and sensory neurons.sensory neurons.
The autonomic nervous system is responsible for The autonomic nervous system is responsible for involuntary actions of the body and contains involuntary actions of the body and contains special motor nerves that control the internal special motor nerves that control the internal organs of the body. Includes two divisions, organs of the body. Includes two divisions, sympathetic and parasympathetic. sympathetic and parasympathetic.
Nerve CellsNerve Cells
Two types of nerve cells, neurons and glial Two types of nerve cells, neurons and glial cells (aka neuroglia cells).cells (aka neuroglia cells).
Neurons are communication cells and the Neurons are communication cells and the functional units of the nervous system. functional units of the nervous system.
Neuroglia cells are non-conducting cells Neuroglia cells are non-conducting cells that support the nervous system. that support the nervous system.
There are two different types of neuroglia; There are two different types of neuroglia; Schwann cells in the PNS and Schwann cells in the PNS and oligodendrocytes in the CNS. oligodendrocytes in the CNS.
Neuroglia or Glial cellsNeuroglia or Glial cells
Glia is a Greek word that means glue.Glia is a Greek word that means glue. Glial cells support and protect neurons, Glial cells support and protect neurons,
provide them with nutrients and oxygen, provide them with nutrients and oxygen, and provide insulation between neurons. and provide insulation between neurons.
Glial cells are capable of dividing via Glial cells are capable of dividing via mitosis.mitosis.
Oligodendrocytes - Oligodendrocytes - Produce myelin sheath Produce myelin sheath around nerve fibers in the central nervous systemaround nerve fibers in the central nervous system
Schwann cells - Schwann cells - Form myelin sheath in the Form myelin sheath in the peripheral nervous systemperipheral nervous systemWhat do you call a group of brains
who form a singing group at school?
GliomasGliomas
Gliomas are tumors Gliomas are tumors that develop in the that develop in the brain involving the brain involving the glial cells. glial cells.
Most cases of Most cases of malignant brain malignant brain tumors are tumors are gliomas.gliomas.
NeuronsNeurons Neurons are the Neurons are the
oldest and longest oldest and longest cells in the human cells in the human body.body.
Neurons cannot Neurons cannot divide via mitosis but divide via mitosis but current research current research suggests that adults suggests that adults can produce new can produce new neurons in their neurons in their brains from neural brains from neural stem cells. stem cells.
Anatomy of a NeuronAnatomy of a Neuron Cell body: Contains the nucleus, rough Cell body: Contains the nucleus, rough
ER and other organelles. Responsible ER and other organelles. Responsible for the maintenance and daily for the maintenance and daily activities of the cell activities of the cell
Axon: a very long and thin extension of Axon: a very long and thin extension of cytoplasm from the cell body. Carries cytoplasm from the cell body. Carries impulses away from the cell body.impulses away from the cell body.
Dendrites: much smaller cytoplasm Dendrites: much smaller cytoplasm extensions which carry impulses to the extensions which carry impulses to the cell body (receive information)cell body (receive information)
Anatomy of a NeuronAnatomy of a Neuron
Myelin Sheath: a type of insulation that is Myelin Sheath: a type of insulation that is wrapped around the axons of neurons. wrapped around the axons of neurons. Helps reduce signal loss.Helps reduce signal loss.
Schwann Cells: produce the myelin Schwann Cells: produce the myelin sheath. A created by specialized glial sheath. A created by specialized glial cells wrapping themselves around the cells wrapping themselves around the axon.axon.
Nodes of Ranvier: gaps between myelin Nodes of Ranvier: gaps between myelin sheath where the axon is “naked”.sheath where the axon is “naked”.
AnatomyAnatomy
Neurilemma: a very thin membrane Neurilemma: a very thin membrane that can be found surrounding the that can be found surrounding the axons of neurons in the PNS. Helps axons of neurons in the PNS. Helps the neurons to regenerate after the neurons to regenerate after trauma. trauma. Neurons that lack a neurilemma and Neurons that lack a neurilemma and
myelin sheath (grey matter of the brain) myelin sheath (grey matter of the brain) do not regenerate, which means trauma do not regenerate, which means trauma to those neurons is permanent.to those neurons is permanent.
Myelin Sheath on NeuronsMyelin Sheath on Neurons
Functions:Functions: Saves the neuron energySaves the neuron energy Helps neuron maintain itselfHelps neuron maintain itself Speeds up the transmission of impulsesSpeeds up the transmission of impulses Helps damaged or severed axons Helps damaged or severed axons
regenerateregenerate
In multiple sclerosis the sheaths of In multiple sclerosis the sheaths of myelinated neurons of the CNS become myelinated neurons of the CNS become scarred. (pg 414)scarred. (pg 414)
Sensory NeuronsSensory Neurons
Aka afferent neuronsAka afferent neurons Pick up and relay Pick up and relay
information from the information from the external environment external environment to the CNSto the CNS
Found in clusters, Found in clusters, known as ganglia, known as ganglia, outside of the CNS.outside of the CNS. Ears, eyes, skin, nose, Ears, eyes, skin, nose,
tongue, etc.tongue, etc.
Five Types of Sensory NeuronsFive Types of Sensory Neurons
PhotoreceptorsPhotoreceptors: sensory receptors in : sensory receptors in the eye that respond to light.the eye that respond to light.
ChemoreceptorsChemoreceptors: sensory receptors : sensory receptors in your nose and on your tongue that in your nose and on your tongue that respond to or are sensitive to respond to or are sensitive to chemicals.chemicals.
ThermoreceptorsThermoreceptors: sensory receptors : sensory receptors in your skin and hypothalamus that in your skin and hypothalamus that respond to warm or cold temperatures. respond to warm or cold temperatures.
Five Types of Sensory NeuronsFive Types of Sensory Neurons
Mechanoreceptors – sensory receptors that respond to mechanical energy. These receptors detect touch, pressure, vibration, limb position, muscle length, and tension
Pain receptors – sensory receptors that respond to tissue injury and excessive pressure.
Motor NeuronsMotor Neurons
Aka efferent Aka efferent neurons.neurons.
Carry signals from Carry signals from the CNS to effectors.the CNS to effectors. Effectors: muscles, Effectors: muscles,
organs, glands.organs, glands. Produce responses Produce responses
such as movement such as movement and release of and release of hormones.hormones.
InterneuronsInterneurons Neurons between Neurons between
neurons.neurons. Located mostly in the Located mostly in the
spinal cord and brain. spinal cord and brain. (grey matter)(grey matter)
Link sensory and motor Link sensory and motor neurons to each otherneurons to each other
Interpret the messages Interpret the messages picked up bypicked up by sensory sensory neuronsneurons
ReflexesReflexes
Reflex arcReflex arc: a circuit through the spinal : a circuit through the spinal cord consisting of a sensory neuron, cord consisting of a sensory neuron, interneuron and motor neuron.interneuron and motor neuron.
Reflex actions are not carried to the brain, Reflex actions are not carried to the brain, instead they are interpreted in the spinal instead they are interpreted in the spinal cord.cord.
Reflexes help prevent major injury by Reflexes help prevent major injury by reducing the amount of time it takes for the reducing the amount of time it takes for the reaction to happen after the sensory input.reaction to happen after the sensory input.
Reflex Arc ReviewReflex Arc Review
Five basic components of the reflex Five basic components of the reflex arcarc
1.1. ReceptorReceptor
2.2. Sensory neuronSensory neuron
3.3. Interneuron in spinal cordInterneuron in spinal cord
4.4. Motor neuronMotor neuron
5.5. Effector Effector