Human Sensory and Coordination Systems: A Deep Dive
Sensory Receptors in Humans
Receptors are the structures human beings use to detect stimuli.
- Interoceptors: Also known as internal receptors, collect information about the human body’s internal conditions. These receptors, located in the internal environment, mostly respond to chemical stimuli (e.g., oxygen in blood).
- Exteroceptors: Also known as external receptors, provide information from the body’s outside environment and are therefore located on the surface of the body. Sense organs are exteroceptors.
- Proprioceptors: Provide information concerning body parts. These receptors are located in the inner ear’s vestibule and the locomotive system (muscles, tendons, and articulations), respectively. They inform about the relative position and condition of each of the body’s muscles.
The Five Senses
Sight
Sight is the sense through which we detect light stimuli. The eye has photoreceptors.
- Cornea: Transparent membrane that protects the eye.
- Pupil: Black aperture.
- Iris: Colored part that contracts and relaxes.
- Crystalline lens: Focuses (accommodation).
- Optical nerve: Transmits information from the retina to the brain.
Hearing
Hearing allows humans to detect sound. The ear is the sense organ that allows us to detect sound waves through mechanoreceptors.
- Outer ear: Antenna.
- Middle ear: Eardrum, transmits sounds.
- Inner ear: Proprioceptors.
Smell
Smell lets humans detect substances dissolved in the air. Olfactory cells are chemoreceptors found in the olfactory mucosa, connected to the brain.
Taste
Taste lets humans detect certain substances dissolved in liquids found in the oral cavity. Chemoreceptors are found on the surface of the tongue and are called taste buds. The pathway is tongue, sensory nerve, then brain.
Touch
Touch detects stimuli through physical contact with elements in the environment. Receptors are located in the skin and are grouped into:
- Mechanoreceptors: Detect changes in pressure.
- Thermoreceptors: Sensitive to changes in temperature.
- Nociceptors: Sensitive to pain.
Coordinating Systems
Coordinating systems:
- Receive information collected by receptors.
- Interpret the information received and produce an appropriate response.
- Activate the organs required to perform this response.
Nervous System
The nervous system is made up of nerves, the brain, and the spinal cord. It processes the information sent by the receptors and generates fast, short-lived responses. The information is transmitted through nerve impulses.
- Brain
- Spinal cord
- Autonomic (glands, cardiac muscle, smooth muscle)
- Somatic muscle (skeletal muscle)
Endocrine System
The endocrine system is formed by endocrine glands, which, when stimulated, secrete hormones into the bloodstream. Blood carries these chemical signals to target tissues and organs where they trigger slower, long-lasting responses. It coordinates body processes using chemical messengers called hormones (which travel through the blood). Endocrine glands produce and release hormones.
Neurons
Neurons are specialized in producing and transmitting electrical nerve impulses.
- Sensory neurons: Nerve cells that detect external stimuli.
- Relay neurons: Nerve cells linked to other neurons that form networks within the central nervous system.
- Motor neurons: Nerve cells that send responses from the central nervous system to the effectors (synapse).
(Soma), dendrites, axon
A stimulus is detected by receptors. The stimulus is relayed and interpreted by coordination systems. They produce a response. Organisms respond by means of organs and structures called effectors.
Neuron
Fast, short-lasting, electrical.
Endocrine
Glands (organs that produce a substance), slow, long-lasting, hormones.