Types of Receptors and their Functions

Discuss about the Clinical Anatomy Physiology for Veterinary Technicians.

Receptors are cells within the nervous system that are adapted for the detection of stimuli (Moini, 2015). A stimulus can be either internal changes like PH or external changes like a light mainly exist in five categories. The mechanoreceptors detect mechanical stimuli, i.e. touch. The photoreceptors detect light. Chemoreceptor detects chemicals, i.e. salt in food. Thermoreceptor detects heat. The nociceptor detects pain. After the detection, these changes are transformed from normal changes to electrical impulses (Jones K. , 2011).

Their function is to pick the message or the impulses generated by the receptor and transport it to the central nervous system (CNS) (Jones K. , 2011). What happens is that after detection of the stimulus by the receptor, the impulses excite the sensory neuron (Finkel & Whalen, 2014). The sensory neuron the travels with the message to the interneuron within the (CNS).

The integrating center functions as the place where all signals meet. Signals from different receptors come to the integration center, and some could be even holding information that that is responding to different forms of stimuli (Watson & Watson, 2014). The integration center’s output represents the integration of various bits of responses. For simple reflexes, the integration center occurs as a single synapse called a monosynaptic reflex (Moini, 2015).

These neurons carry efferent impulses processed from integration center and takes them to the effector (Plowman & Smith, 2013). The information carried by the motor neuron is more like processed commands carrying specific instructions for the effector ordering it to change a particular activity (Colville & Bassert, 2015). The path taken by a motor neuron is referred to as the efferent pathway which generally means carrying or moving away. In this case, it means carrying away the impulses generated by the integrating center.

Effectors are either muscles or glands. The axons from the motor neuron make contact with muscle fibers. The section of the contact is known as the neuromuscular junction (Finkel & Whalen, 2014). When the effector receives the instruction, the muscles contract and the opposing muscles relax.

The pituitary gland is the master gland. It releases the followings hormones that;

Growth hormone: Controls growth of body tissues and differentiation in cells (Plowman & Smith, 2013).

Thyroid stimulating hormone (TSH): This hormone that triggers the thyroid gland to secrete thyroid hormone (Colville & Bassert, 2015).

Adrenocorticotrophic hormone (ACTH):  Triggers adrenal glands to secrete the adrenal cortex hormones (Jones K. , 2011).

The Role of Neurons in the Nervous System

Gonadotrophic hormones:   Compose of luteinizing hormone (LH) and the follicle-stimulating hormone (FSH) (Jones & Lopez, 2013). LH charge with stimulation of production of sperms and FSH controls the production of ovaries in women.

Prolactin: The hormone concerned with milk production.

Melanocyte: It stimulates melanocytes in the skin, the cells that make the pigment melanin, which makes the skin’s dark to protect it from the damaging UV rays of the sun  (Jones K. , 2011)..

Anti-diuretic hormone: It intensifies reabsorption of water in the kidneys.

Oxytocin: Excites the contractions of the uterus and ejection of milk from the breasts.

The thyroid gland secretes the hormone thyroxin. This hormone contains iodine.  Thyroxin helps in the regulation of metabolic rate and growth in the body (Colville & Bassert, 2015). They also release calcitonin hormone that lowers calcium concentration in the blood.

Parathyroid glands secrete Parathyroid hormone. This hormone works together with calcitonin in the balancing of calcium levels.

The adrenal medulla secretes the hormones adrenalin and noradrenalin which increase the heartrates in the cases of emergency (Jones K. , 2011). The cortex secretes the steroid hormones for the regulation of the use of carbohydrates, salt and balancing water. The cortex also releases small quantities of sex hormones or androgens.

The Pancreas produces has cells (Islets of Langerhans) which produce somatostatin, insulin, and glucagon (Moini, 2015). The insulin drops the level of blood sugar while glucagon stimulates the conversion of glycogen to glucose. The somatostatin regulates the secretion of both insulin and glucagon.

The ovaries are for the production of estrogen and progesterone which are female hormones (Macdonald, 2011). Estrogen helps in the maturing of the ovum, keeps the hair and skin in good condition, and sustains other female sexual features (Plowman & Smith, 2013). The progesterone deals maintenance of the pregnancy. The testes release testosterone, a male hormone. This hormone works for the production of sperms and development of male sexual features.

Neurons are the body’s building blocks for its communication system. As the neurons are spread throughout the body, their network allows them to move signals between body parts and the brain (Moini, 2015). Apart from that, the human nervous system has two parts. The first one is the CNS which is made up of the brain and the spinal cord. The CNS utilizes neurons for its communication. The main work of the CNS is to process different body’s sensation from both internal and external environment  (Colville & Bassert, 2015). The CNS then processes that information and sends instructions to the rest of the body organs to take the necessary action. For example, when it is hot, the CNS would send instructions for quick removal of the hand from the fire. If it is moderate heat, the CNS instructs the body to move away from heated room.

The Structure and Function of the Central Nervous System

The other part of the nervous system is the peripheral nervous system (PNS) which made up nerves and a network of nerves across the body. These nerves and the nerve networks are mainly bundles of neuron cells’ axons (Finkel & Whalen, 2014). The PNS further divides into somatic and autonomic nervous system. The somatic system communicates sensory information, and it controls the voluntary body actions and movements like walking away from heat in the previous example. This system is made up of the sensory neurons, and they carry impulses to the CNS. The motor neurons then carry information from the CNS to other muscle fibers. The autonomic nervous system controls the involuntary functions such as the heartbeat, digestion, respiration, and blood pressure (Watson & Watson, 2014). Besides, it also manages the emotional responses like crying or sweating. The autonomic system further divides into sympathetic systems and parasympathetic systems. The sympathetic system manages the body’s reactions to emergencies. For instance, when scared, the heart and the breathing rates rise.  The parasympathetic system counters the sympathetic system. It reverses the responses sympathetic system. For example, it calms the body down after an emergency. The heart-rate and breathing go down.

The endocrine system also functions as the body’s communication tool. Unlike the nervous system, this one utilizes glands that are spread across the body (Watson & Watson, 2014). The glands secrete hormones which the body uses for the regulation of different factors such as blood pressure, metabolism, growth, and digestion. Among other glands, the most important ones are the pineal gland, pituitary, hypothalamus, the thyroid, ovaries, and testes. All these glands work uniquely to alter specific parts of the body.

Both systems are connected by a structure in the brain called the hypothalamus. This structure has is composed of nuclei which control the level of each behavior (Moini, 2015). The hypothalamus controls basic operations like sleep, thirst, hunger, sex and other emotions such as stress responses. It also regulates pituitary glands which are the master of other glands.

Label	Organ
A	Fallopian Tubes
B	Suspensory ligament of ovary
C	Ovary
D	Corpus
E	Cervix
F	Vagina
G	Uterus Endometrium
H	Uterus Myometrium
I	Uterus Perimetrium

The vagina is an expandable tubular organ with mucous membrane, and it lies between the urinary bladder and rectum (Heffner & Schust, 2010). The vagina joins the internal female reproductive organs with the external genitals. Its main roles in the reproduction are to receive the penis, receive the sperm after ejaculation, act as a passage for the menses during a menstrual cycle and act as a passage for the fetus at the time of birth (Macdonald, 2011).

The Peripheral Nervous System and its Divisions

In the adults, the vaginal canal is between three to four inches long (Heffner & Schust, 2010). It has muscles that stretch to control the diameter.

The uterus is also called the womb. It is a pear-shaped organ that is above the vagina or in the pelvic cavity, in the exteriors of the rectum, and above the urinary bladder (Rogers, 2010). The uterus adjusts its position depending on the gravity, posture, size, and shape. It provides an area for processes of menstruation, fertilization, implantation, and growth of the fetus (Heffner & Schust, 2010).  The uterus measures between two and three inches before the first pregnancy but remains larger after the first pregnancy. It then turns smaller again after menopause. The uterine wall is composed of three layers; the endometrium is the innermost layer, myometrium is the muscular-middle layer, and the outer layer is called perimetrium.

The cervix lies at the lower parts of the uterus. It is the part that links the vagina and the uterus. One of the functions of the cervix is to lead the sperm to the uterus. Another role is to allow exit of the menstrual discharge and allowing passage of the fetus at the time of birth (Jones & Lopez, 2013).  The cervix is made up of fibrous connective tissue. It is also coated with mucosa, and it has an alkali environment. The role of the alkali surface is to protect the sperm from being damaged by the acid in the vaginal environmen (Jones & Lopez, 2013)t. The cervix also has mucus-secreting glands. These glands produce mucus that no sperm can penetrate before the ovulation. The consistency of this mucus changes to allow the sperm to swim when ovulation happens (Macdonald, 2011).  Meanwhile, the mucus-secreting glands start storing live sperm for a period of two to three days.

The corpus refers to the main body or the wider region of the uterus. This region is highly muscularized, and it enlarges to accommodate the growing size of the fetus (Jones & Lopez, 2013). The inner lining is called the endometrium. The region undergoes multiple cyclic changes due to the changing levels of the hormones coming from the ovaries. During a menstrual cycle, it thickens and allows the fertilized egg to enter the uterus (Rogers, 2010). In the case of fertilization, the embryo attaches itself to the uterus walls and becomes implanted in the endometrium (Rogers, 2010). At the time of labor, the corpus walls contract and start pushing the baby towards the vagina via the cervix. Where there is no fertilization takes place, the large part of it comes out, and this becomes the bleeding during a monthly period.

The Master Gland: Pituitary Gland and its Hormones

The oviducts are also referred to as the fallopian tubes.  The oviducts are hollow and have a cylindrical structure that that between seven to ten centimeters long (4 inches). It has a diameter of approximately 0.7 cm (Jones & Lopez, 2013). The near end of the oviduct next to the ovary has a funnel-shaped portion. This part is called the oviductal infundibulum, and its opening where the eng enters is called the ostium. The infundibulum has fingerlike projections (fimbriae) at the edges. During ovulation, the infundibulum captures the egg (ovum) and passes it to the oviduct (Rogers, 2010). Since the oviductal lining has cilia, it beats the egg pushing it towards the uterus. Along the oviduct there is a there is a widened section called the oviductal ampulla. Ahead of this section, there is a narrower part called the oviductal isthmus (Macdonald, 2011). Lastly, after oviductal isthmus, there is the other part which attaches to the uterine wall called the intramural oviduct. With its cilia, the oviduct brings the ovum towards the uterus and the sperm towards the ovary. This movement is accomplished via ciliary action and peristalsis. When both meets, fertilization occurs, and the fertilized eggs start moving into to the uterus.

The ovaries are the two glands that resemble unshelled almonds located on either side of the pelvic cavity. The ovaries are pearl-colored, oval-shaped structures. The ovaries have no attachment to the oviduct though they hang some several nearby. These ligaments hold the ovaries in position. The two primary functions of the ovaries are to secrete estrogen and progesterone hormones (Heffner & Schust, 2010). Another function is to develop and release the ovum. Also, the ovaries work as the bridge between the female reproductive system and the endocrine system of the body (Rogers, 2010). That is, they secrete the female hormones under the control or the management of the pituitary glands.

A	Urinary blabber
B	Prostate gland
C	Ejaculatory duct
D	Urethra
E	Testis
F	Vas deferns
F	Epididymis Testis
G	Penis
I	Seminal vesicle

Testes are male glands that produce sex hormones. They have an oval shape with about 4.0cm length and 2.5cm width. The testes execute two roles. The first role is the production of sperm. The second role is the secretion of the testosterone, which is the main male sex hormone (Heffner & Schust, 2010). Inside the testicles are the seminiferous tubules which produce sperm.  Like the ovaries in the female reproductive system, the testes link the male body system with the endocrine system (Finkel & Whalen, 2014). That is, the pituitary glands produce the FSH and LH. These are the hormones that instruct testes to secrete testosterone.

The vas deferens or the duct system looks like a cord. Its work is to transport the produced sperm from the epididymis. Each duct runs from the testis to the prostate. It then extends to the urethra where it becomes the ejaculatory ducts (Rogers, 2010). It has other elements such as the nerves and blood vessels and together they form spermatic cord.

These are the vesicles whose role is to release seminal fluid that carries the nutrients for the sperm. The two seminal vesicles secrete fluid a fluid that has, fructose, prostaglandins, and alkaline properties (Jones & Lopez, 2013). The fructose provides energy for the sperm while the prostaglandins provide mobility. The alkaline properties protect the sperm from vaginal and urine acid.

 The prostate gland releases the prostatic fluid which has alkaline properties. The prostate glands connect to the ejaculatory glands that lead to the urethra via several tiny ducts.

The penis serves to function. In reproduction, it erects during sexual delivers semen into the female external organ, the vagina. The semen comes through the urethra hat extends to the tip of the penis and ejaculate out. In excretory system, the penis passes the urine out of the body through urethra opening.

References

Colville, T. P., & Bassert, J. M. (2015). Clinical Anatomy and Physiology for Veterinary Technicians – E-Book (3 ed.). Elsevier Health Sciences.

Finkel, R. S., & Whalen, K. (2014). Pharmacology (6 ed.). Wolters Kluwer.

Heffner, L. J., & Schust, D. J. (2010). The Reproductive System at a Glance. Wiley-Blackwell.

Jones, K. (2011). Neurological Assessment E-Book: A Clinician’s Guide (2 ed.). Elsevier Health Sciences.

Jones, R. E., & Lopez, K. H. (2013). Human Reproductive Biology (4 ed.). Elsevier Science.

Macdonald, S. (2011). Mayes’ Midwifery E-Book: A Textbook for Midwives (14 ed.). Elsevier Health Sciences.

Moini, J. (2015). Anatomy and Physiology for Health Professionals (2 ed.). Jones & Bartlett Learning.

Plowman, S. A., & Smith, D. L. (2013). Exercise Physiology for Health Fitness and Performance (4 ed.). Wolters Kluwer Health.

Rogers, K. (2010). The Reproductive System (Human Body (Rosen Educational Publishing)). Rosen Education Service.

Watson, C. C., & Watson, C. (2014). Human Physiology. Jones & Bartlett Learning, LLC.