Exp 3

DATE:________ Experiment: 01 Objects: To observe superficial reflexes in a human subject. Theory Neuron Neurons are nerve cells that are constantly sending signals to your brain, muscles and glands. You have over 100 billion neurons in your brain sending signals. The signals help the different parts of your body communicate with each other. Neurons send chemical signals called neurotransmitters, and they work quickly to help you react to everything going on around you. Resting Membrane Potential A resting potential is the normal state of an axon. It's like the neuron is at rest, and therefore it's called the resting potential. During a resting potential, there is a higher concentration of potassium ions inside the axon and a higher concentration of sodium ions outside the axon. This makes the inside of the axon have a more negative charge at rest than the outside of the axon. Action potential Upon the beginning of action potential, If a neuron has a message that needs to be sent, sodium channels in the axon open, and sodium rushes into the axon. This makes the inside of the axon more positive relative to the outside. This sets off the chain reaction, as more sodium channels open up a little further down the axon, causing that part of the axon to become more positive, and so on. Reflex Action The nervous system produces involuntary or automatic responses to stimuli using nervous relays called reflex arcs. Reflex arcs always encompass a sensory receptor, sensory neuron, motor neuron, and an effector; an interneuron may also connect the sensory and motor neurons. The neurons of the reflex arc may be located in the spine or brainstem, but reflexes are programmed without input from higher brain regions (e.g., temporal lobe, frontal lobe). Have you ever been cooking and accidentally bumped your hand against a hot pan? Likely, before you could even register what happened, you jerked your hand away, maybe even clutching your hot skin. When something like this happens, it feels like you simply react to the situation automatically, without thinking. Although biologically this might seem impossible, it's exactly what really happens in your nervous system.

Although we think of the brain as being the boss of all of our actions and thoughts, some actions actually take place without the brain's input. These reactions are called reflexes. Reflex Arc: The process of the sensory neuron carrying the stimulus to the spinal column and brain, and then the brain sending a message to the motor neuron is called a reflex arc. Components of Reflex Arc: Receptor: the receptor responds to an electrical signal. Afferent pathway: this pathway sends the action onto the integrating centre (sensory neuron). Integrating centre: this is typically the nervous system and is where all of the action potentials are processed. Once the information is processed the integrating centre determines how the body should respond. Efferent pathway: the response then travels through this pathway to the effector organ (motor neuron). Effector organ: this organ carries out the response to all of the above. The organ responding is usually a muscle or gland in the body. Cranial Nerves Your cranial nerves are pairs of nerves that connect your brain to different parts of your head, neck, and trunk. There are 12 of them, each named for their function or structure. Each nerve also has a corresponding Roman numeral between I and XII. This is based off their location from front to back. For example, your olfactory nerve is closest to the front of your head, so it’s designated as I. Their functions are usually categorized as being either sensory or motor. Sensory nerves are involved with your senses, such as smell, hearing, and touch. Motor nerves control the movement and function of muscles or glands.

Spinal Nerves Your spinal nerves come out from the sides of your spine, or backbone. The spine has 33 vertebrae or irregularly shaped bones, and inside these bones is the spinal cord, which the spinal nerves branch out from.

Your spine has four curves and is divided into five regions, based on where the curves occur. These regions are the: cervical (neck), thoracic (chest/trunk), lumbar (low back), sacral (pelvis) and the coccygeal (tail bone). Each region of the spine has a specific function and a different number of vertebrae. Cervical Nerves: 8 cervical (C1-C8) nerves emerge from the cervical spine; cervical means of the neck (there are 8 cervical nerves, but only 7 cervical vertebra) Thoracic Nerves: 12 thoracic (T1-T12) nerves emerge from the thoracic spine; thoracic means of the chest Lumbar nerves: 5 lumbar (L1-L5) nerves emerge from the lumbar spine; lumbar means from the lower back region Sacral Nerves: 5 sacral (S1-S5) nerves emerge from the sacral bone; sacral means of the sacrum, the bony plate at the base of the vertebral column Coccygeal Nerve: 1 coccygeal nerve emerge from the coccygeal bone; coccygeal means of the coccyx, the tailbone

Procedure: Name of the reflex Corneal reflex

Consensual Light reflex

Abdominal reflex

Procedure & Mechanism

Result

The corneal reflex test (blink test) Blinking of eyes examines the reflex pathway involving cranial nerves V and VII. Classically the provider lightly touches a wisp of cotton on the patient’s cornea. This foreign body sensation should cause the patient to reflexively blink. The reflex is consensual: Normally light that is directed in one eye produces pupil constriction in both eyes. The direct response is the change in pupil size in the eye to which the light is directed (e.g., if the light is shone in the right eye, the right pupil constricts). The consensual response is the change in pupil size in the eye opposite to the eye to which the light is directed (e.g., if the light is shone in the right eye, the left pupil also constricts consensually). The pupillary light reflex allows the eye to adjust the amount of light reaching the retina and protects the photoreceptors from bright lights. The iris contains two sets of smooth muscles that control the size of the pupil Make the subject lie down Contraction of comfortably on a bed in the supine abdominal muscles position. Uncover the abdomen and see that his abdominal muscles are well relaxed. With a blunt object gently stroke on the abdominal skin from lateral to the medial aspect in all four quadrants. Observe the contraction of the abdominal muscles resulting in deviation of umbilicus towards the area stimulated. A normal positive response usually involves a contraction of the abdominal muscles, and the umbilicus moving towards the source of the stimulation.

Centre involved Cranial nerves V and VII

Thoracic nerves 6 to 12

Plantar Reflex

The plantarreflex is a reflex elicited when the sole of the foot is stimulated with a blunt instrument. The reflex can take one of two forms. In normal adults, the plantar reflex causes a downward response of the hallux (flexion). An upward response (extension) of the hallux is known as the Babinski response or Babinski sign, named after the neurologist Joseph Babinski. The presence of the Babinski sign can identify disease of the spinal cord and brain in adults, and also exists as a primitive reflex in infants.[

Lumbar Flexor: the toes curve nerve 5, down and inwards, Sacral nerve and the foot inverts; 1 this is the response seen in healthy adults . Extensor:the hallux d orsiflexes, and the other toes fan out; this is Babinski's sign, which indicates damage to the central nervous system if elicited in an adult, but normal reflex if elicited in infants

Observation: Name of The Reflex

Result Observed

Significance of Each Reflex: ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ Result: ______________________________________________________________________________ ______________________________________________________________________________