Nervous System (Nervous systems consist of circuits of neurons and…
Nervous systems consist of circuits of neurons and supporting cells
The enteric division consists of networks of neurons in the digestive tract, pancreas, and gallbladder that regulate secretion and peristalsis.
Activation of the parasympathetic division causes opposite responses that promote calming and a return to self-maintenance functions (“rest and digest”).
The motor system consists of neurons that carry signals to skeletal muscles. Regulation of smooth and cardiac muscles by the autonomic nervous system is involuntary. The sympathetic division is responsible for arousal and energy generation.
Astrocytes have the most diverse set of functions: They provide structural support for neurons and regulate the extracellular concentrations of ions and neurotransmitters.
Gray matter consists of mainly neuron cell bodies, dendrites, and unmyelinated axons. White matter contains bundled axons with myelin sheaths, making them whitish.
Both are filled with cerebrospinal fluid, formed in the brain by filtration of arterial blood.
The cavity of the nerve cord forms the narrow central canal of the spinal cord and the ventricles of the brain.
The spinal cord acts independently as part of the simple nerve circuits that produce reflexes, the body’s automatic responses to stimuli
The brain and spinal cord of the vertebrate CNS are tightly coordinated.
In more complex animals, the axons of multiple nerve cells may be bundled to form nerves.
Many nervous system disorders can be understood in molecular terms
Parkinson’s disease is a motor disorder including muscle tremors, poor balance, a flexed posture, and a shuffling gait.
The incidence of Alzheimer’s disease is age related, rising from about 10% at age 65 to about 35% at age 85.
Bipolar disorder involves swings of mood from high to low and affects about 1% of the world’s population.
Individuals affected by major depressive disorder have periods in which once enjoyable activities provide no pleasure and provoke no interest.
About 1% of the world’s population suffers from schizophrenia, a severe mental disturbance characterized by psychotic episodes in which patients have a distorted perception of reality.
Changes in synaptic connections underlie memory and learning
Long-term potentiation (LTP), a lasting increase in the strength of synaptic transmission, involves a presynaptic neuron that releases the excitatory neurotransmitter glutamate.
To retain knowledge of a name or phone number requires activation of mechanisms of long-term memory.
We constantly check what is happening against what just happened a few moments ago, holding information in short-term memory and releasing it if it becomes irrelevant.
The nervous system has a great capacity to be remodeled in response to its own activity, this is called neural plasticity.
The cerebral cortex controls voluntary movement and cognitive functions
Some of the sensory input to the cerebral cortex comes from groups of receptors clustered in dedicated sensory organs, such as the eyes and nose
The left hemisphere is more adept at math and logical operations, while the right hemisphere is dominant in the recognition of faces and patterns, spatial relations, and nonverbal thinking.
The cerebrum is the largest structure in the human brain and exhibits regional specialization.
Such differences in hemisphere function in humans are lateralization.
The vertebrate brain is regionally specialized
The brain structure with the most important role in storage of emotional memory is the amygdala, an almond-shaped mass of nuclei located near the base of the cerebrum.
In mammals, circadian rhythms are coordinated by a group of neurons in the hypothalamus called the suprachiasmatic nucleus or SCN.
Circadian rhythms rely on a biological clock, a molecular mechanism that directs periodic gene expression and cellular activity.
Arousal and sleep are controlled in part by the reticular formation, a diffuse network of neurons in the core of the brainstem.