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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

I learned that anatomy is the study of the human structure. the smaller ones can be observed by the assistance of a microscope
Hawa Reply
what are the disciplines of anatomy
Bint Reply
what is the difference between anatomy and physiology
Addai Reply
the structure of human body the function of human body
anatomy is study of structure off the body and physioly is the study off function of body eg git
study of structure of the human body and study of function off the body eg git
nice 👍
what does anatomy deal with
anatomy deala with study of human structure eg human skeltal syatem
explain proximal in terms of anatomy body planes and give examples
don't know
anyone here MLT
anatomy is the study structure of the human body. physiology is the study of function and mechanism of the body
I don't get the consent wrll
Joana Reply
what's pathology
the science of the causes and effects of diseases
yes dear you right
is the study of the abnormalities and how they affect body functions often causing illness
type of anatomy
what are cells
Cells are the basic structural and functional unit of all living organisms which they exist from pre-existing cells that self replicate on their own.
Cell is the structural , Function and heritability unit of life .
What is the function of liver
liver helps in detoxification of toxic substances in our body and metabolism of drugs
what is septum sacroti
What drugs use to treat liver diseases
like ursodioxycholic acid
liver disease medications depend on the type of liver disease..cirrhosis of the liver, no alcoholic liver disease, hep b, hep c.
what causes thyphoid
Maria what is carcinoma
What is ursodioxycholic acid
No alcoholic liver diseases and help b, help c
carcinoma is a type of cancer. it starts in the tissue lining the organs such as the liver or kidneys
describe the urine formation
Sarah Reply
Body water
the urine formation is described as the wrist fluid that comes out of body
glomerular filtration, reabsorption, secretion.
good Hellen kehn
is it wast fluids or wrist?
how many bones does human have?
about the urine formation Baldwin asked that is it wast fluid or wrist that comes out from the body
waste fluids.. Tubular Reabsorption: Glucose, Amino acids, Proteins, Vitamins, Lactate, Urea, Uric acid, NA+, K+, Ca2+, Mg2+, Cl-, HCO3-, H20 Tubular Secretions: Urea, Uric acids, Creatinine, H+, NH4+, K+ Each different section of the Nephron has a different mineral that absorbs or secrets
thank you Emmi
No problem, Happy to help.. I have a photo of exactly which area does what but I don't think I can attach on this platform..
***socratic.org/questions/how-is-urine-produced-in-the-kidneys On this web page if you stroll down, there is a picture describing it. its my favorite diagram. Very clear and informative
how can we access another platform to share more information
if you copy and paste that url.. it'll take you to the website I mentioned
define what is a port of entry for microorganisms?
A port of entry is specific to that microorganism. for example, a bacterial infection of the urinary tract would have the vaginal area as the port of entry.
droplets from one person to another is one 👍
or you can say that a viral microbe/flu would have a port of entry through the nasal cavity, mouth, or eyes because it is part of the respiratory system.
in children more then 206 and in young man 206
emmi,you losing me .,. please make me clear on the question👆
nice Emmi
children have 300
is female circumcision possible
noo, there is no possibility for circumcision in females
Carcinoma is abnormal division of cells in the body without control
female circumcision is technically considered a human rights violation and done in some countries where they partially remove the external female genitalia.
then again tubal ligation, I believe is like female circumcision. they tie or burn your tubes and you won't be able to have kiddos. so yes, its possible.
ok and so I mean not having kids .just kidding there I'm going to sleep.
Maria madam thank you for sharing this information
what is single cell
Jimmy Reply
A unicellular organism, also known as a single-celled organism, is an organism that consists of a single cell, unlike a multicellular organism that consists of multiple cells. ... Many eukaryotes are multicellular, but many are unicellular such as protozoa, unicellular algae, and unicellular fungi.
Why is important to check if the blood if compatible before transfusion ?
Kelvin Reply
to avoid cases of intravenous clupping in blood which can be fatal....bcos blood is incopartable
Thank you.good answer
what are the clinical significant of thyroid gland
Jennifer Reply
what is a metabolism?
Kheth Reply
Metabolism is the sum total of all the chemical processes in the body. It is divided into an anabolic(building up) and catabolic(breaking down) metabolism)
Oh ok
sir what is constructive and destructive metabolism
is anyone
Describe the system s that maintain the internal environment of a human body
Nora Reply
an organism is a living being that had a cellular structure and that can independently perform all physiological functions needed for life.
Nwecho Reply
a tissue is a group of similar cells that work together to perform a particular function
chemical level, cellular level, tissue level, organs level, organ systems, organisms
Nwecho Reply
they're reproduction but also produces hormones dus they're endocrine system
cells are smallest independent functional unit of a living organism
an organ is an anatomically distinct structure of the body composed of two or more tissue
an organ system is a group of organs that work together to perform a major function.
Structural Organization of the human body.
very good
What is a cavity
Isaac Reply
Permanently damaged areas in teeth that develop into tiny holes
what is meant by epithelial tissue
What is the difference between regional anatomy and systematic anatomy?
Andrew Reply
Regional anatomy is the study of the interrelationships of all of the structures in a specific body region, such as the abdomen. ... In contrast, systemic anatomy is the study of the structures that make up a discrete body system—that is, a group of structures that work together to perform a unique
Pls is that all
regional anatomy studies structures that contribute to specific body region example the thoracic region while systematic anatomy studies structures that contribute to specific body systems example respiratory system

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Source:  OpenStax, Anatomy & Physiology. OpenStax CNX. Feb 04, 2016 Download for free at http://legacy.cnx.org/content/col11496/1.8
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