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The Basics Of The Human Nervous System
Patrick Hinshawon 29 April 2011
Transcript of The Basics Of The Human Nervous System
Patrick Hinshaw What is the nervous system? -Organ system of specialized
cells called "neurons" Made up of two parts: Central
and peripheral nervous system. Central Nervous System What is it, what does it do? "Portion of Nervous system that consists brain and spinal cord." Integrates the information that it recieves and coordinates the activities of all parts of the body The central nervous system.. is the control center for the entire body, majority
of it is located in the dorsal cavity (brain) and spine Peripheral Nervous System What is it, what does it do? "The portions of the nervous
system outside the CNS" The peripheral nervous system.. is a branch of the CNS that allows the CNS to communicate with the rest of the body is divided into two parts, The somatic and
autonomic nervous system Somatic nervous System Autonomic nervous system Consists of cranial and spinal nerve fibers
that connect to the CNS to the skin and
skeletal muscles. Oversees all conscious
activities. (voluntary nervous control) Connects CNS to viscera such as the heart,
stomach, intestines, and glands. (involuntary
nervous control) Together, the CNS and PNS provide
3 basic functions: -Sensory function -Motor Function -Integrative function Sensory Function Sensory functions derive from sensory receptors on ends of peripheral nerves. These sensory receptors..
- Gather information/detect changes inside and outside of the body.
- Monitor external enviromental factors, such as light, sounds and temp Generally, sensory receptors convert enviromental information into images our brain can interpret. This is known as "Integrative function". Motor functions are the functions
that actually carry the nerve
impulses to its destination. Some basic parts of the nervous system And now on to something else.. Neurons http://www.youtube.com/watch?v=RHKY_kiHk0g Neurons are a nervous tissue consisting of masses of nerve cells
Neurons are the structural and functional units of the nervous system.
They transmit information in electrochemical messages called
Impulses travel down nerve fibers to other cells/neurons outside the NS.
A nerve is a bundle of nerve fibers
Vary considerably in size
Each have a cell body/tubular nerve fibers Neuron Structure Consists of organelles such as mitochondria, lysosomes, and a network of fine threads called neurofibrils which are in the
Contains two types of nerve fibers: Axons and Dendrites A neuron can contain many dendrites, but only one axon Axons Conducts nerve impulses away from cell body.
begins as a single fiber, but may branch off at the end into fine extensions to connect with other cells
Dendrites Usually short and highly branched
These fibers are the neurons main receptive suface to cummunicate with other neurons Types of Neurons 1. Sensory neurons: They carry impulses from the
peripheral body parts into the brain or spinal cord. Each SN either has specialized receptor ends on dendrites or receptor cells. Most are either unipolar, while some are bipolar. 2. Interneurons: These are located within the brain and spinal cord. They are multipolar and
connect other neurons to eachother. Pretty much, these neurons direct the impulses to the appropraite parts of the brain for processing. 3. Motor Neurons: These neurons carry nerve impulses out of the brain and spinal cord to effectors. they stimulate muscle and glands to release secretions Another type of cell is very important to the nervous system.. The neuroglial cell They fill empty spaces, support neurons, provide framework, and carry on phagocytosis. Types: - Microglial cells: Scattered throughout CNS. they support neurons and neutralize bacteria/cellular debris
- Oligodendrocytes: Found on nerve fibers, form myeling on brain and spine.
- Astrocytes: usually found between things like neurons, and blood vessels. These usually provide structural framework, and help to create scar tissue once an injury to the NS occurs.
- Ependymal cells: Forms epithelial membrane that covers some brain parts and forms linings within the brain. The Synapse Neurons never touch, they travel from neuron to neuron by passing through a junction called a synapse. The gap between neurons is called the synaptic cleft.
Process of crossing a synapse is called synaptic transmission.
Axons are one way because they have synaptic knobs, which contain synaptic vesicles that release nuerotransmitters. These NT's tell the neuron specific things it needs to accomplish.
NT's produce either two reactions.. Excitatory and Inhibitory Actions NT's that increase permeability to sodium ions and trigger nerve impulses are said to be excitatory. They generally promote a nerve impulse
NT's that decrease membrane permeability to sodium ions are said to be inhibitory. They make it less likely that the impulse will actually fire. Nerve Pathways The nerve pathway is the route a nerve impulse travels through the nervous system A simple nerve pathway is called a reflex arc. It's the basis for the reactions we call reflexes. Reflexes Reflexes are automatic subconscious responses to stimuli. They maintain
homeostasis by regulating/controlling heart rate, digestion and blood pressure. There are 2 basic types of reflexes The knee jerk reflex and the withdrawal reflex The Knee-jerk reflex Simple reflex that only involves 2 neurons, a sensory and a motor.
Striking the patellar ligament just below the patella starts this reaction. Stretch receptors are stimulated, and impulses travel to the spinal cord. They then travel back by way of a motor neuron back to the knee, causing the reaction.
This reflex helps to maintain upright posture. The Withdrawal Reflex This type of reaction occurs when a person encounters something painful.
Skin receptors activate, impulse is sent to spinal cord. The impulse is redirected by an interneuron to a reflex center, then sent back to the muscle by motor neurons.
The muscle contracts.
Unconsiously and instantly, you put yourself out of harms way. This is a protective reflex. The Brain The brain is the center of the nervous system. it contains about 100 billion neurons and an uncountable amount of nerve fibers connecting eachother. It controls all autonomous functions. Divided into 3 major sections: -Cerebrum -Cerebellum -Brain Stem