Nervous System Flashcards
Nervous system
-Senses, interprets, and issues commands as a response to conditions in the body’s environment
-this process is made possible by very complex communication system organized as a grid of neurons
-messages are sent across the plasma membrane of neurons through a process called action potential
-these messages occur when a neuron is stimulated past a necessary threshold
-the stimulations occur in a sequence from the stimulation point of one neuron to its contact with another neuron
-at the point of contact, called a chemical synapse, a substance is released that stimulates or inhibits the action of the adjoining cell
-this network fans out across the body and forms the framework for the nervous system
-the direction of the information flows depends on the specific organizations of nerve circuits and pathways
Three functional types of neurons
Sensory neurons
Motor neurons
Interneurons
Sensory neurons
Transmit signals to the central nervous system (CNS) from the sensory receptors associated with touch, pain, temperature, hearing, sight, smell, and taste
Motor neurons
Transmit signals from the CNS to the rest of the body such as by signaling muscles or glands to respond
Interneurons
Transmit signals between neurons
-ex. Interneurons receive transmitted signals between sensory neurons and motor neurons
In general, a neuron consists of three basic parts
Cell body
axon
dendrites
Cell body (soma)
Contains the nucleus of the neuron
Axon
-Transmits the impulses away from the cell body
-the axon is insulated by oligodendrocytes and the myelin sheath with gaps known as the nodes of Ranvier
-the axon terminates at the synapse
CNS
Consists of brain and spinal cord
[CNS]
Spinal cord
-Spinal cord is encases in the bony structure of the vertebrae, which protects and supports it
-it’s nervous tissue functions mainly with respect to limb movement and internal organ activity
-major nerve tracts ascend and descend from the spinal cord to the brain
[CNS]
Brain
Brain consists of the hindbrain, midbrain, and forebrain
[CNS]
Brain: HINDBRAIN
The hindbrain includes the medulla oblongata, cerebellum, and pons
[CNS]
Brain: MIDBRAIN
-The midbrain integrates sensory signals and orchestrates responses to these signals
-The midbrain is associated with vision, hearing, motor control, sleep/wake, arousal (alertness), and temperature regulation, acting as a sort of relay station for auditory and visual information.
[CNS]
Brain: FOREBRAIN
The forebrain includes the cerebrum, thalamus, and hypothalamus
[CNS]
Brain: FOREBRAIN—CEREBRAL CORTEX
The cerebral cortex is a thin layer of gray matter covering the cerebrum
[CNS]
Brain lobes
The brain is divided into four main lobes, the frontal lobe, the parietal lobe, the occipital lobe,and the temporal lobe
[CNS]
Brain lobes: FRONTAL
The frontal lobe is located in the front of the brain is responsible for a short term and working memory and information processing as well as decision-making, planning, and judgment
[CNS]
Brain lobes: PARIETAL
The parietal lobe is located slightly toward the back of the brain and the top of the head and is responsible for sensory input as well as spatial positioning of the body
[CNS]
Brain lobes: OCCIPITAL
-The occipital lobe is located at the back of the head, just above the brain stem
-this lobe is responsible for visual input, processing, and output, specifically, nerves from the eyes enter directly into this lobe
[CNS]
Brain: CEREBELLUM
-The cerebellum plays a role in the processing and storing of implicit memories
-specifically, for those memories developed in classical-conditioning learning techniques
-the role of the cerebellum was discovered by exploring the memory of individuals with damaged cerebellums -these individuals were unable to develop stimulus responses when presented via a classical conditioning technique
-researchers found that this was also the case for automatic responses
-ex. when these individuals were presented with a puff of air into their eyes, they did not blink, which would have been a naturally occurring and automatic response in an individual with no brain damage
[CNS]
Brain: BRAINSTEM
-the posterior area of the brain that is connected to the spinal cord is known as the brainstem
-the midbrain, the pons, and the medulla oblongata are the three parts of the brain stem
-information from the body is sent to the brain through the brainstem, and information from the brain is sent to the body through the brainstem
-the brainstem is an important part of respiratory, digestive, and circulatory functions
[CNS]
Brain: MIDBRAIN
-the midbrain lies above the pons and medulla oblongata
-the parts of the midbrain include the tectum, the tegmentum, and the ventral tegmentum.
-The midbrain is an important part of vision and hearing
-the pons comes between the midbrain and the medulla oblongata
-information is sent across the pons from the cerebrum to the medulla and the cerebellum
-the medulla oblongata (or medulla) is beneath the midbrain and the pons
-the medulla oblongata is the piece of the brainstem that connects the spinal cord to the brain
-so, it has an important role with the autonomic nervous system in the circulatory and respiratory system
PNS
Consists of the nerves and ganglia throughout the body and include sympathetic nerves that trigger the “fight or flight” response, and the parasympathetic nerves which control basic body functions
PNS
Sympathetic nerves
Control fight or flight response
PNS
Parasympathetic nerves
Control basic body function
Autonomic Nervous System [ANS]
-Maintains homeostasis within the body
-controls the functions of the internal organs, blood vessels, smooth muscle tissues, and glands
-this is accomplished through the direction of the hypothalamus, which is located above the midbrain
[ANS]
Hypothalamus
-hypothalamus controls the ANS through the brainstem
-with this direction from the hypothalamus, the ANS helps maintain a stable body environment (homeostasis) by regulating numerous factors including heart rate, breathing rate, body temperature, and blood pH
[ANS]
Consists of two divisions
The sympathetic nervous system and the parasympathetic nervous system
[ANS]
Sympathetic nervous system
-Controls the body‘s reaction to extreme, stressful, and emergency situations
-ex. the sympathetic nervous system increases the heart rate, signals the adrenal glands to secrete adrenaline, triggers the dilation of pupils, and slows digestion
[ANS]
Parasympathetic nervous system
-counteracts the effects of the sympathetic nervous system
-ex. the parasympathetic nervous system decreases the heart rate, signals the adrenal glands to stop secreting adrenaline, constrict the pupils, and returns the digestion process to normal
Somatic Nervous System [SNS]
-Controls the five senses and the voluntary movement of skeletal muscle
-this system has all of the neurons that are connected to sense organs
-efferent (motor) and afferent (sensory) nerves health of somatic nervous system operate the senses and the movement of skeletal muscle
[SNS]
Efferent nerves
Bring signals from the central nervous system to the sensory organs and the muscles
[SNS]
Afferent nerves
-bring signals from the sensory organs and the muscles to the central nervous system
-the somatic nervous system also performs in voluntary movements which are known as reflex arts
Reflex
-Simplest act of the nervous system
-an automatic response without any conscious thought to a stimulus via the reflex arc
Reflex arc
-Simplest nerve pathway, which bypasses the brain and is controlled by the spinal cord
-ex. the classic knee-jerk response (patellar tendon reflex), the stimulus is the reflex hammer hitting the tendon, and the response is the muscle contracting, which jerks the foot upward
-the stimulus is detected by sensory receptors, and a message is sent along a sensory (afferent) neuron to one or more interneurons in the spinal cord
-the interneurons transmit this message to a motor (efferent) neuron, which carries the message to the correct effector (muscle)
