The action potential is repeatedly regenerated along the length of the axon. –An action potential achieved at one region of the membrane is sufficient to depolarize a neighboring region above threshold. Thus triggering a new action potential. The refractory period assures that impulse conduction is unidirectional. Nerve impulses propagate themselves along an axon
Excitatory postsynaptic potentials (EPSP) depolarize the postsynaptic neuron. –The binding of neurotransmitter to postsynaptic receptors open gated channels that allow Na + to diffuse into and K + to diffuse out of the cell. Neural integration occurs at the cellular level
Inhibitory postsynaptic potential (IPSP) hyperpolarize the postsynaptic neuron. –The binding of neurotransmitter to postsynaptic receptors open gated channels that allow K+ to diffuse out of the cell and/or Cl- to diffuse into the cell.
Acetylcholine- slows heart rate; PNS Glutamate- most prevalent neurotransmitter in the brain Aspartate- in CNS GABA- inhibitory neurotransmitter Glycine- inhibitory neurotransmitter Norepinephrine- awakening from deep sleep Epinephrine- increase heart rate Dopamine- movement of skeletal muscles Seratonin- sensory perception, temp regulation, mood, sleep Nitric oxide- may play a role in memory and learning Enkephalin- inhibit pain impulses by suppressing release of substance P Substance P- enhances perception of pain tyrosine
The ability of cells to respond to the environment has evolved over billions of years
Nerve nets. Nervous systems show diverse patterns of organization
With cephalization come more complex nervous systems.
Parasympathetic and Sympathetic Nervous System: A subdivision of the PNS Not under conscious control Work antagonistically Controlled by medulla oblongata and hypothalamus Peripheral nervous system that supplies stimulation via motor nerves to smooth and cardiac muscle and to glands
neurotransmitter is norepinephrine, fight or flight E = exercise, excitement, emergency, and embarrassment neurotransmitter is acetylcholine D = digestion, deification, diuresis (urinating)
Emotions. –In mammals, the limbic system is composed of the hippocampus, olfactory cortex, inner portions of the cortex’s lobes, and parts of the thalamus and hypothalamus. Mediates basic emotions (fear, anger), involved in emotional bonding, establishes emotional memory –For example, the amygdala is involved in recognizing the emotional content of facial expression.
Thalamus Relay center for sensory tracts from the spinal cord to the cerebrum. Contains centers for sensation of pain, temperature, and touch. Involved with emotions and alerting or arousal mechanisms.
Hypothalamus autonomic control center- blood pressure, rate and force of heart contraction, center for emotional response and behaviorautonomic control center- blood pressure, rate and force of heart contraction, center for emotional response and behavior body temperaturebody temperature water balance and thirstwater balance and thirst sleep/wake cyclessleep/wake cycles appetiteappetite sexual arousalsexual arousal control of endocrine functioning:control of endocrine functioning: Acts on the pituitary gland through the release of neurosecretions. Regulates:
Pons Connects the two halves of the cerebellum. Regulates breathing.
Medulla Oblongata Composed of nerve tracts to and from the brain (these tracts cross over left to right and right to left) May be regarded as an extension of the spinal cord Almost all of the cranial nerves arise from this region
Medulla Oblongata Contains control centers for many subconscious activities Respiratory rate Respiratory rate Heart rate Heart rate Arteriole constriction Arteriole constriction Swallowing Swallowing Hiccupping Hiccupping Coughing Coughing Sneezing Sneezing
Cerebellum Controls and coordinates muscular activity. Important in equilibrium, posture and movement.