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The sensory input

This diagram shows the first step of the previous figure. A hand is placed under flowing water, causing a sensory receptor in the index finger to send a nerve impulse down the arm, to the spinal cord.
Receptors in the skin sense the temperature of the water.

The neurotransmitter diffuses across the short distance of the synapse and binds to a receptor protein of the target neuron. When the molecular signal binds to the receptor, the cell membrane of the target neuron changes its electrical state and a new graded potential begins. If that graded potential is strong enough to reach threshold, the second neuron generates an action potential at its axon hillock. The target of this neuron is another neuron in the thalamus    of the brain, the part of the CNS that acts as a relay for sensory information. At another synapse, neurotransmitter is released and binds to its receptor. The thalamus then sends the sensory information to the cerebral cortex    , the outermost layer of gray matter in the brain, where conscious perception of that water temperature begins.

Within the cerebral cortex, information is processed among many neurons, integrating the stimulus of the water temperature with other sensory stimuli, with your emotional state (you just aren't ready to wake up; the bed is calling to you), memories (perhaps of the lab notes you have to study before a quiz). Finally, a plan is developed about what to do, whether that is to turn the temperature up, turn the whole shower off and go back to bed, or step into the shower. To do any of these things, the cerebral cortex has to send a command out to your body to move muscles ( [link] ).

The motor response

This diagram shows the later steps of Figure 12.13. A hand is placed under flowing water. The axon of a motor neuron travels down the forearm and then branches as it reaches the hand. Each branch synapses with a different skeletal muscle in the hand. The synapse between the axon branches and the muscle is a neuromuscular junction. An impulse travelling down the motor neuron will cause the skeletal muscles to contract, resulting in muscle movement. In this case, the movement results in the person adjusting the faucet dials to change the temperature of the water.
On the basis of the sensory input and the integration in the CNS, a motor response is formulated and executed.

A region of the cortex is specialized for sending signals down to the spinal cord for movement. The upper motor neuron    is in this region, called the precentral gyrus of the frontal cortex    , which has an axon that extends all the way down the spinal cord. At the level of the spinal cord at which this axon makes a synapse, a graded potential occurs in the cell membrane of a lower motor neuron    . This second motor neuron is responsible for causing muscle fibers to contract. In the manner described in the chapter on muscle tissue, an action potential travels along the motor neuron axon into the periphery. The axon terminates on muscle fibers at the neuromuscular junction. Acetylcholine is released at this specialized synapse, which causes the muscle action potential to begin, following a large potential known as an end plate potential. When the lower motor neuron excites the muscle fiber, it contracts. All of this occurs in a fraction of a second, but this story is the basis of how the nervous system functions.

Career connections


Understanding how the nervous system works could be a driving force in your career. Studying neurophysiology is a very rewarding path to follow. It means that there is a lot of work to do, but the rewards are worth the effort.

The career path of a research scientist can be straightforward: college, graduate school, postdoctoral research, academic research position at a university. A Bachelor’s degree in science will get you started, and for neurophysiology that might be in biology, psychology, computer science, engineering, or neuroscience. But the real specialization comes in graduate school. There are many different programs out there to study the nervous system, not just neuroscience itself. Most graduate programs are doctoral, meaning that a Master’s degree is not part of the work. These are usually considered five-year programs, with the first two years dedicated to course work and finding a research mentor, and the last three years dedicated to finding a research topic and pursuing that with a near single-mindedness. The research will usually result in a few publications in scientific journals, which will make up the bulk of a doctoral dissertation. After graduating with a Ph.D., researchers will go on to find specialized work called a postdoctoral fellowship within established labs. In this position, a researcher starts to establish their own research career with the hopes of finding an academic position at a research university.

Other options are available if you are interested in how the nervous system works. Especially for neurophysiology, a medical degree might be more suitable so you can learn about the clinical applications of neurophysiology and possibly work with human subjects. An academic career is not a necessity. Biotechnology firms are eager to find motivated scientists ready to tackle the tough questions about how the nervous system works so that therapeutic chemicals can be tested on some of the most challenging disorders such as Alzheimer’s disease or Parkinson’s disease, or spinal cord injury.

Others with a medical degree and a specialization in neuroscience go on to work directly with patients, diagnosing and treating mental disorders. You can do this as a psychiatrist, a neuropsychologist, a neuroscience nurse, or a neurodiagnostic technician, among other possible career paths.

Chapter review

Sensation starts with the activation of a sensory ending, such as the thermoreceptor in the skin sensing the temperature of the water. The sensory endings in the skin initiate an electrical signal that travels along the sensory axon within a nerve into the spinal cord, where it synapses with a neuron in the gray matter of the spinal cord. The temperature information represented in that electrical signal is passed to the next neuron by a chemical signal that diffuses across the small gap of the synapse and initiates a new electrical signal in the target cell. That signal travels through the sensory pathway to the brain, passing through the thalamus, where conscious perception of the water temperature is made possible by the cerebral cortex. Following integration of that information with other cognitive processes and sensory information, the brain sends a command back down to the spinal cord to initiate a motor response by controlling a skeletal muscle. The motor pathway is composed of two cells, the upper motor neuron and the lower motor neuron. The upper motor neuron has its cell body in the cerebral cortex and synapses on a cell in the gray matter of the spinal cord. The lower motor neuron is that cell in the gray matter of the spinal cord and its axon extends into the periphery where it synapses with a skeletal muscle in a neuromuscular junction.

Questions & Answers

list down all the hormones secreted by adrenal gland
Odong Reply
The amount of blood pumped by the left ventricle of the heart in one contraction.
Javid Reply
how we can calculate the cardiac output
and how do we calculate the strock valume
stroke volume is not all the blood contained in the left ventricle; normally, only about two-thirds of the blood in the ventricle is expelled with each beat.
Cardiac output 5.5 l S. V 68.75 ml H. R 80bpm
If we consider SV 70, end systolic vol is about 15% of total(approx always) out of a total of 80-85 ml only 70ml is pumped per systole
what is macrophages?and its function
Sajjad Reply
macrophages they are white blood cells that engulf dead cells in the body
what is power stroke?
no idea
what is the stroke volume of heart?
If an autoimmune disorder targets the alpha cells, production of which hormone would be directly affected?
Samantha Reply
what is a muscle?
Gideon Reply
A band or bundle of fibrous tissue in a human or animal body that has the ability to contract, producing movement in or maintaining the position of parts of the body
what's endolphthamities and panophthalmities?
fluid around the brain
louise Reply
what ?
cerebro spinal fluid
The brain and spinal cord are surrounded by a clear fluid called cerebrospinal fluid (CSF). This fluid is produced and stored in cavities in the brain called ventricles. It circulatesaround the brain, moving from ventricle to ventricle. ... Hydrocephalus is a condition in which there is too much CSF
what is hydrocphalus
aminul Reply
Google krlena na madarchod yha maa chudwa rha ha sabko notification bhjke
when cerebrospinal fluid produce în the brain, i.e. brain ventricles, is to abundent in the brain and is not trăind out of the brain. as a consequence this lichid pute mechanical pressure oñ the brain and it pushes the cerebrum tissue. as a consequence this pressure on the neuronscan cause neurologi
cal disfunctions, for example clinical headache
. It is posible to drainout the fluid through a device dalles shunt,as i remember.
but where are also home medicinsfor decreasing the production of cerebrospin.fluid etc
there are some medicines that can decrease the production of csf
a neurologist advice is needed
i wrote some medicines NOT home medicines. it is a serious condition and specialized medical advice is needed. of course also general medical knowledge may be helpful, but not enough, a specialist is neede
if anyone help me in physiology
Radika Reply
i am BSN student of first year which book is best for physiology
i am BSN student of first year which book is best for physiology
ross and wilson anotomy and physiology
it's 1 book for anotomy and physiology it's best for bs nursing
yes Ross and wilson physiology is better for study
I'm also the student of bs nursing
I study guiton and hall &ganong
I'm also midwif help me be the best book for midwif
what ia the function of indocrine system
salam all friend
help me with this question; explain at least five emergency acute pain found in fundamental emergency medicine
Fascial compartment of forearm
what's a tissue?
Mwape Reply
a group of cells with the same function
tissue is a group of cells that perform the same functions.
explain a bit about a tissue
A tissue is made up of cells that are similar in shape and perform the same function, for instance brain cells form up a brain tissue. Whereas a group of tissues that perform the same function form an organ... so in this case the brain which is the organ is formed as a result of brain tissues.
what is gross anatomy
the branch of anatomy that deals with the structure of organs and tissues that are visible to the naked eye.
1.To know how the structures functions. 2.To easily identify the micro structures and the macro structures. 3.To be able to explain that anatomy is the study of the structures and physiology is the study of how the structures functions
Abban Reply
Describe the two classes of hormones (3 with subclasses) and how they affect their target cells.
Shalaeha Reply
what is control centre
Gohil Reply
Angie The larger air passage of the lung is
Angie Reply
guys help to make me understand the structure of the skin
Olokojo Reply
the skin has three layers epidermis,dermis,and subcutaneous tissue
guys what is esrf
End Stage of Renal Failure
what's the meaning of OPD
Out Patient Department
the skin has the assesory structures.that is, sebaceous glands, sweat glands, hairs, nails,blood vessels and lymph vessels.
define cell and give it's brief description of the orgenelles
Manish Reply
a cell is a basic unit of life
what about philosophy
the organelle is a membrane bound structure in the cell that performs a particular function
Cell.Is a basic functional unit of life. it has the organelles, Golgi apparatus, smooth endoplasmic membrane, rough endoplasmic reticular,Lysosomes, mitochondrial and others.

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