The nervous system has three main functions: sensory input, integration in the central nervous system, and motor output. It is composed of neurons, which are cells that transmit electrical and chemical signals. Neurons have dendrites, a cell body, and an axon ending in synaptic terminals. Information flows from sensory neurons to interneurons to motor neurons in a reflex arc or longer pathways. At the synapse, an electrical signal becomes a chemical signal using neurotransmitters. The peripheral nervous system controls voluntary and involuntary functions and connects to the central nervous system, which integrates sensory input and coordinates motor output through structures like the brainstem, cerebellum, and cerebrum.
Sensory Neurons – picks up the stimuli (nerve impulse) and carries it to the spinal cord and brain.Interneurons- Found within the brain and spinal cord. Relays the message between the sensory neurons and the motor neurons. Motor Neurons – transfers impulses away from the brain to the spinal cord
The action potential travels from one location in the cell to another, but ion flow across the membrane occurs only at the nodes of Ranvier. As a result, the action potential signal jumps along the axon, from node to node, rather than propagating smoothly, as they do in axons that lack a myelin sheath.
Function of Dendrites. In order for neurons to become active, they must receive action potentials or other stimuli. Dendrites are the structures on the neuron that receive electrical messages. These messages come in two basic forms: excitatory and inhibitory.
The Cell body (soma) is the factory of the neuron. It produces all the proteins for the dendrites, axons and synaptic terminals and contains specialized organelles such as the mitochondria, Golgi apparatus, endoplasmic reticulum, secretory granules, ribosomes and polysomes to provide energy and make the parts, as well as a production line to assemble the parts into completed products.
Powepoint presentation on the Nervous System, its function and composition. Nerves and neurons - Nerve impulses- Synapse- Reflex action- Reflex arc. - Notes on the eye. links to further study
Sensory Neurons – picks up the stimuli (nerve impulse) and carries it to the spinal cord and brain.Interneurons- Found within the brain and spinal cord. Relays the message between the sensory neurons and the motor neurons. Motor Neurons – transfers impulses away from the brain to the spinal cord
The action potential travels from one location in the cell to another, but ion flow across the membrane occurs only at the nodes of Ranvier. As a result, the action potential signal jumps along the axon, from node to node, rather than propagating smoothly, as they do in axons that lack a myelin sheath.
Function of Dendrites. In order for neurons to become active, they must receive action potentials or other stimuli. Dendrites are the structures on the neuron that receive electrical messages. These messages come in two basic forms: excitatory and inhibitory.
The Cell body (soma) is the factory of the neuron. It produces all the proteins for the dendrites, axons and synaptic terminals and contains specialized organelles such as the mitochondria, Golgi apparatus, endoplasmic reticulum, secretory granules, ribosomes and polysomes to provide energy and make the parts, as well as a production line to assemble the parts into completed products.
Powepoint presentation on the Nervous System, its function and composition. Nerves and neurons - Nerve impulses- Synapse- Reflex action- Reflex arc. - Notes on the eye. links to further study
The nervous system is made up of the central nervous system and the peripheral nervous system. The central nervous system (CNS) is made up of the brain and spinal cord. The brain controls most body functions, including awareness, movements, sensations, thoughts, speech and memory.
Nervous system ( anatomy and physiology)Ravish Yadav
the topic contain function of nervous system, classification of nervous system, neurons anatomy, structural classification of neurons, functional classification of neurons, nerve impulse
1. Chapter 48 ~49 Nervous System
I. The Nervous system
A. Primary Functions:
1.Sensory input from a sensory receptor via the PNS
2.Integration in the CNS (central nervous system)
3.Motor output to effector cells (muscle or gland cells) that respond via the PNS (peripheral
nervous system)
B. Structural Unit of The Nervous System
1. A neuron is composed of a cell body, dendrites, an axon
a. The axon is coated in the Myelin sheath for support and insulation
b. The axon ends with the synaptic terminal where neurotransmitter is released
2. The Synapse is the junction between the neuron and its effector cell or the next neuron.
C. Functional Organization
1. For detecting sensory stimuli:
1.Sensory neurons convey information to spinal cord
2. For information integration:
1.Interneurons
3.For a response:
1. Motor neurons convey signals to effector cells
4. A reflex arc is a simple, automatic response between a sensory neuron and a motor neuron sometimes via a
ganglion
II. How Neurons Work
A. All cells have an electrical charge difference across their membranes which results in a membrane
potential.
Arises from intracellular/extracellular ionic concentration difference
K+ diffuses out (Na+ in); large anions cannot follow….selective permeability of the plasma
membrane
Net negative charge of about -70mV
B. An Action Potential sends an electrical message
1. Neurons and muscle are excitable cells that can change membrane potentials
a. They are normally at their resting potential~ the unexcited state
2. Gated ion channels open/close in response to stimuli.
These include photoreceptors in the eye; vibrations in air (sound receptors); and chemical
(neurotransmitters for interneurons in the CNS)
2. 3. Graded Potentials depend on the strength of the stimulus and can result in:
a. Hyperpolarization (outflow of K+); increase in electrical gradient; cell becomes more
negative
b. Depolarization (inflow of Na+); reduction in electrical gradient; cell becomes less negative
2. A depolarization may trigger an action potential, or nerve impulse, it is an all or none event.
C. The Chemical Synapse
A. The pathway:
1. The presynaptic cell is the transmitting cell
2. The postsynaptic cell is the receiving cell
3. The synaptic cleft is a gap that separates the two cells. This is where the neurotransmitter is
released.(chemical signal)
At this site, the electrical message is converted into a chemical message.
(Some organisms possess electrical synapses where the action potential simply continues on its way via a
GAP JUNCTION.-Crabs, lobsters.)
The nervous system has two divisions:
The PNS or Peripheral Nervous System The CNS or Central Nervous System
includes the nerves that control the includes the brain and the spinal cord
voluntary and involuntary processes of the which synthesize all input and coordinate
body. all output.
III. The Vertebrate PNS
A. The Peripheral Nervous System is composed of cranial nerves and spinal nerves. It has two functional
divisions:
1.Autonomic division controls involuntary actions.
2.Somatic division controls voluntary actions.
A.The Brainstem controls essential life activities(autonomic)
Houses the medulla oblongata, and the pons which control homeostasis, movement coordination,
and conduction of information to the higher brain centers.
B. The Cerebellum coordinates muscular movements
C. The Cerebrum is the largest and most complex portion of the brain. Hearing, taste, speech, vision,
smell, memory and other centers are located here.