SOMATIC AND SPECIAL SENSES (Anatomy and Physiology Correlation for NHPC Exam)

 INTRODUCTION

The sensory system enables the body to perceive, interpret, and respond to changes in the internal and external environment. It consists of sensory receptors, neural pathways, and sensory centers in the brain.Sensations are classified into:1. Somatic (General) Senses – widely distributed across the body.2. Special Senses – localized in specialized organs.



SOMATIC (GENERAL) SENSES

Somatic senses arise from receptors in the skin, muscles, joints, and viscera. They provide information about touch, pressure, temperature, pain, and body position.



Pathways of Somatic Sensation

- Dorsal Column Pathway: carries fine touch, vibration, and proprioception.  Pathway: Receptors → Dorsal root ganglion → Medulla → Thalamus → Somatosensory cortex (postcentral gyrus).- Spinothalamic Tract: carries pain and temperature.  Pathway: Receptors → Dorsal horn of spinal cord → Crosses to opposite side → Thalamus → Cortex.


Clinical Correlation

- Loss of touch/proprioception → lesion in dorsal column.- Loss of pain/temperature → lesion in spinothalamic tract.- Diabetic neuropathy → damage to peripheral receptors → decreased sensation.- Referred pain → visceral pain perceived in somatic areas due to shared pathways.


SPECIAL SENSES

Special senses are highly specialized and localized in distinct organs: Vision, Hearing, Equilibrium, Taste, and Smell.


Vision

Anatomy: Eyeball with three layers – fibrous (sclera, cornea), vascular (choroid, ciliary body, iris), and nervous (retina). Physiology: Light enters cornea → pupil → lens → retina. Rods (dim light), cones (color). Optic nerve transmits to occipital lobe.Clinical: Myopia, Hypermetropia, Cataract, Glaucoma, Color blindness.


Hearing and Equilibrium

Anatomy: External ear (pinna, canal), Middle ear (ossicles), Inner ear (cochlea for hearing, semicircular canals for balance). Sound → Tympanic membrane → Ossicles → Oval window → Cochlea → Hair cells → Auditory nerve → Temporal lobe.

Equilibrium: Static (vestibule) and Dynamic (semicircular canals).



Taste (Gustation)

Receptors: Taste buds on papillae. Nerves: Facial (VII) – anterior 2/3, Glossopharyngeal (IX) – posterior 1/3, Vagus (X) – epiglottis.

Primary tastes: Sweet, Sour, Salty, Bitter,


Smell (Olfaction)

Olfactory epithelium in nasal cavity roof contains receptors.

Impulses via Olfactory nerve (I) → Bulb → Temporal lobe.


Clinical: Anosmia, Hyposmia.



Integration and Perception

All sensory signals reach the sensory cortex for perception. The thalamus acts as a relay center except for smell, which goes directly to the cortex.



Key Exam Points

• Receptors: mechanoreceptors, thermoreceptors, nociceptors, proprioceptors.• Tracts: Dorsal column (fine touch), Spinothalamic (pain/temp).• Retina: Rods and cones.• Organ of Corti: Hearing receptor.• Semicircular canals: Dynamic balance.• Taste cranial nerves: VII, IX, X.• Olfactory nerve (I): Smell.• Thalamus lesion: sensory loss opposite side.






Please leave your valuable comments.



Comments

Post a Comment

Popular posts from this blog

Anatomy & Physiology – NHPC Exam Guide Part 1: Expanded Illustrated Edition

  Table of Contents 1. Chapter 1: Definition and Scope 2. Chapter 2: Levels of Organization 3. Chapter 3: Anatomical Terminology 4. Chapter 4: Overview of Body Systems 5. Chapter 5: Homeostasis 6. Chapter 6: Embryology – Introduction Chapter 2: Levels of Organization The human body is organized into a hierarchy of structural levels, each building upon the previous one. This concept helps explain how microscopic events affect overall human health. • Chemical Level: Atoms and molecules form the basis of all living matter. Essential molecules like proteins, lipids, and carbohydrates participate in metabolic reactions. • Cellular Level: Cells are the basic units of structure and function. Each cell has organelles performing specific roles, e.g., mitochondria for energy. • Tissue Level: Tissues are groups of similar cells that perform a specific function. Examples: epithelial tissue (lining), muscle tissue (movement). • Organ Level: Organs are made of two or more tissues working togethe...
Read more

Anatomy & Physiology – NHPC Exam Guide Part 2: Human Development and Ageing Author: SB Thapa

  Table of Contents 1. 1. Chapter 1 – Introduction to Human Growth and Development 2. 2. Chapter 2 – Prenatal Development 3. 3. Chapter 3 – Postnatal Development 4. 4. Chapter 4 – Adulthood and Maintenance of Health 5. 5. Chapter 5 – Ageing and Senescence 6. 6. Chapter 6 – Common Age-Related Disorders 7. 7. Chapter 7 – Death and Dying Chapter 1 – Introduction to Human Growth and Development Growth refers to the quantitative increase in body size, mass, or organ dimensions, while development involves qualitative changes, including functional and behavioral maturity. Together, they represent the dynamic processes through which a single-celled zygote becomes a mature human capable of reproduction and adaptation. The stages of human life include prenatal, neonatal, childhood, adolescence, adulthood, and old age. Each stage is influenced by genetic, hormonal, nutritional, and environmental factors. For instance, thyroid and growth hormones regulate physical growth, while environmental s...
Read more

Cardiovascular System

  1. Heart Anatomy – In-Depth 1.1 External Anatomy Located in the middle mediastinum , apex pointing to 5th intercostal space midclavicular line Surfaces: Sternocostal : RA & RV predominantly Diaphragmatic : LV and some RV Pulmonary (left) : LV impression on left lung Borders: Right: RA Left: LV and auricle Superior: Base – LA and great vessels Pericardium: Fibrous pericardium : tough outer layer, attached to diaphragm and sternum Serous pericardium: Parietal layer: lines fibrous pericardium Visceral layer (epicardium): on heart surface Pericardial cavity:  15–50 mL of lubricating fluid Clinical correlation:  Pericardial effusion → cardiac tamponade; auscultation changes 1.2 Internal Anatomy Chambers & Wall Thickness: | Chamber | Wall Thickness (mm) | Relative Function ||---------|-------------------|-----------------|| RA | 2–3 | Low pressure reservoir || RV | 3–5 | Pumps to pulmonary circulation || LA | 2–4 | Receives pulmonary venous blood || LV | 8–12 | Pump...
Read more