Transcript The Nervous System

Chapter 48-49
• The anatomy of a neuron.
• The mechanisms of impulse transmission in a neuron.
• The process that leads to release of neurotransmitter, and what
happens at the synapse.
• The components of a reflex arc and how they work.
• The organization and function of the major parts of the nervous
system.
• One function for each major brain region.
• The location and function of several types of sensory receptors.
• How skeletal muscle contracts.
• Cellular events that lead to muscle contratction
• Functional unit of the nervous system
• Dendrites: cell extensions that receive
incoming messages from
other cells
• Axon: transmit messages to other cells
• Covered in myelin sheath (Schwann cells or oligodendrocytes) to speed up
transmission
• Synapse: is the junction between axons and dendrites
• Neurotransmitters (NT): chemical messengers (drugs) released from
the synaptic terminals of the axon which bind to receptors of the
receiver (another neuron, muscle cell, or gland)
• Acetylcholine, dopamine, serotonin, GABA, etc.
• Central nervous system (CNS) = brain & spinal cord
• Peripheral nervous system (PNS) = everything else including
motor and sensory neurons
• Nerves are clusters of neurons
Types of neurons:
• Sensory receptors: receive information from the environment
• Sensory neurons: send signals from receptors to CNS
• Interneurons: brain and parts of the spinal cord
• Motor neurons: transmit signals to effectors (muscles, glands)
• Membrane potential:
difference in electrical
charge across the cell
membrane
• Resting potential:
neuron at rest (-70mV)
• All or none response to
stimulus
• If membrane potential
reaches threshold (55mV) AP will fire
1. Resting state
2. Depolarization
3. Depolarization >=
threshold  AP
4. Repolarization
5. Undershoot
• APs propagate down the axon
• It jumps from one node of Ranvier to the next (saltatory
conduction)
• The signal is revitalized at every node
• At the synapse the signal continues via electrical or chemical
(NT) stimulus
• Stimulus can be inhibitory or excitatory
• Simplest response to
stimulus
• Receptor  sensory
neuron  interneuron
(spinal cord)  motor
neuron  effector
(reaction)
• The brain finds out later
• Brain and spinal cord
• Cells bathed in cerebrospinal fluid (CSF) for nutrients and
cleansing
• Grey matter = neuron cell bodies and unmyelinated axons
• White matter = myelinated axons
• Neural glial cells (glia) support neurons:
• Astrocytes provide nutrients for neurons
• Oligodendrocytes make myelin sheath in the CNS (Schwann cells in the
PNS)
• Divided into two subdivisions:
1. Somatic nervous system: muscles you control
2. Autonomic nervous system: automatic muscle and organ control
subdivided into two more categories
1.
2.
Sympathetic division: fight or flight mechanism
Parasympathetic division: rest and digest
• Compartmentalized:
• Brainstem = medulla oblongata, pons,
and midbrain
• Primitive brain = primitive functions like
homeostasis and breathing
• Cerebellum: coordinated motor movement
• Thalamus: main center for all sensory and
motor information
• Hypothalamus: regulates homeostasis and
basic survival behaviors
• Cerebrum: two hemispheres with grey
over white matter
• Cerebral cortex: Higher order thinking occurs
here (largest in mammals) and voluntary
movement
• Corpus callosum: white matter enabling
communications of the two hemispheres
Perception: brain recognition of stimulus
Reception: receptor detects a stimulus
• Mechanoreceptors: stimulated by physical stimuli
• Thermoreceptors: stimulated by temperature
• Chemoreceptors: chemical stimulation (taste and smell)
• Electromagnetic receptors (photoreceptors): detect various
forms of energy (light, electricity, or magnetism)
• Pain receptors: detect too much heat or chemicals released from
dying cells