The Nervous System Unit 7 (Drugs that affect the brain (Heroine can cause…
The Nervous System Unit 7
Major Functions of the Nervous System
he nervous system collects sensory input from the body and external environment and respond appropriately to the sensory input.
Neurons are specialized cells of the nervous system that transmit signals throughout the body.
The neurons that transmit this signal to the muscles are called motor neurons. Motor neurons are not just limited to sending signals to muscles, they can also send signals to glands within our body and stimulate or inhibit secretion of various substances that then carry out or regulate many body functions
reflex reaction is an automatic, involuntary reaction to an unexpected stimulus
motor nerves: These nerves conduct impulses from the CNS and PNS to the muscles, organs and glands' effecting what happens in those tissues
Three main functions are sensory input, motor output, and information processing.
The nervous system takes in information through our senses, processes the information and triggers reactions, such as making your muscles move or causing you to feel pain
Major divisions and subdivisions of the nervous system
The peripheral nervous system includes cranial nerves and spinal nerves. It provides communication lines between the CNS and the rest of the body.
The sensory division includes somatic and visceral sensory nerve fibers, it conducts impulse receptors to the CNS
Motor division includes the motor nerve fibers, it conducts impulses from the CNS of effectors.
The Somatic nervous system is voluntary motor fibers, it conducts impulses from the CNS to skeletal muscles.
The autonomic nervous system includes involuntary motor nerve fibers, it conducts impulses from the CNS to cardiac muscle, smooth muscle, and glands.
The Central Nervous system includes the brain and spinal cords, it integrates and controls.
The sympathetic divisions mobilize body systems during activity.
The parasympathetic division converses energy and promotes house keeping functions during the rest.
Tissues (structure & function of a neuron)
Neurons are highly specialized nerve cells that generate and conduct nerve impulses. A typical neuron consists of dendrites, the cell body, and an axon.
Dendrites are responsible for responding to stimuli, they receive incoming signals towards the cell body
The axons are responsible for transmitting impulses over long distances from cell body.
In the peripheral nervous system, Schwann cells are neuroglia cells that support neuronal function by increasing the speed of impulse propagation.
Neuroglia in the CNS include astrocytes, microglial cells, ependymal cells and oligodendrocytes. In the PNS, satellite cells and Schwann cells are the two kinds of neuroglia.
Astrocytes are shaped like a star and are the most abundant glial cell in the CNS. They have many radiating processes which help in clinging to the neurons and capillaries.
Classification of neurons
The cell body is the portion of the cell that surrounds the nucleus and plays a major role in synthesizing proteins.
Dendrites are short, branched processes that extend from the cell body. Dendrites function to receive information, and do so through numerous receptors located in their membranes that bind to chemicals.
An axon is a large process that extends from the cell body at a point of origin-called the axon hillock-and functions to send information.
Once an axon reaches a target, it terminates into multiple endings, called axon terminals. The axon terminal is designed to convert the electrical signal into a chemical signal in a process called synaptic transmission.
Multipolar neurons are defined as having three or more processes that extend out from the cell body. They comprise of more than 99% of the neurons in humans, and are the major neuron type found in the CNS and the efferent division of the PNS
Bipolar neurons have only two processes that extend in opposite directions from the cell body. One process is called a dendrite, and another process the axon.
Unipolar neurons have a single, short process that extends from the cell body and then branches into two more processes that extend in opposite directions.
Drugs that affect the brain
Heroine can cause a feeling of sedation and well bein, dopamine is released without inhibitions.
Ecstasy gives the reward pathway addictive pathways and transports serotonin out of the cell.
Marijuana slows down movement and gives a relaxing feeling. the cannabinoid receptors turn off inhibitory neurotransmitter release.
Methamphetamine makes the user feel intense pleasure, dopamine is pumped out of the cell and into the synapses
Alcohol can impact decision making, impulse control, and memory formation, it prevents the glutamate from exiting the cell.
Cocaine controls voluntary movement an the reward pathway, dopamine binds continuously and over the receptors over stimulate the cell.
LSD evokes startle response to unexpected stimulus , it interacts with particular receptors and sometimes inhibits them and other times excites them.
Opiods are a stimulant that can make you lose consciousness, withdraws symptoms, and stomach aches.
Inhalants are considered depressants, they can cause sudden death, brain damage, seizures, and hallicinations.
A neurotransmitter influences a neuron in one of three ways: excitatory, inhibitory or modulatory.
An excitatory transmitter promotes the generation of an electrical signal called an action potential in the receiving neuron, while an inhibitory transmitter prevents it.
The first neurotransmitter to be discovered was a small molecule called acetylcholine. It plays a major role in the peripheral nervous system, where it is released by motor neurons and neurons of the autonomic nervous system.
Glutamate is the primary excitatory transmitter in the central nervous system
Noradrenaline is another monoamine, and is the primary neurotransmitter in the sympathetic nervous system where it works on the activity of various organs in the body to control blood pressure, heart rate, liver function and many other functions.
Neurotransmitters are often referred to as the body’s chemical messengers. They are the molecules used by the nervous system to transmit messages between neurons, or from neurons to muscles.
Communication between two neurons happens in the synaptic cleft
Compare & contrast the autonomic nervous system; the parts of the
One difference between a somatic reflex, such as the withdrawal reflex, and a visceral reflex, which is an autonomic reflex, is in the efferent branch
The output of a somatic reflex is the lower motor neuron in the ventral horn of the spinal cord that projects directly to a skeletal muscle to cause its contraction.
The output of a visceral reflex is a two-step pathway starting with the preganglionic fiber emerging from a lateral horn neuron in the spinal cord, or a cranial nucleus neuron in the brain stem, to a ganglion
Many of the inputs to visceral reflexes are from special or somatic senses, but particular senses are associated with the viscera.