Nervous system and homeostasis

Nervous system

Responsible for coordinating all the systems of the body, including the maintenance of a steady internal environment (homeostasis).

Homeostasis

The state in which the body’s systems work together to maintain a constant internal environment by detecting and responding to any changes in the external environment or internal environment

Sensory Input

Sensory receptors monitor changes occurring both inside and outside the body and transmit afferent signals towards the CNS

Integration

Sensory receptors monitor changes occurring both inside and outside the body and transmit afferent signals towards the CNS

Integration

The brain and spinal cord process, interpret and analyse incoming sensory signals, deciding on the appropriate physiological action or conscious response required.

Motor output

The central nervous system initiates a response by transmitting efferent nerve impulses to effector organs, including skeletal muscle, cardiac muscle, smooth muscle or secretory glands

Function of the Receptors

1. Detect the change in a variable (stimulus) and send a signal to the control centre

Function of the Control centre

Receives the signal from the receptors, compares the variable to a set point and sends a signal to the effector

Function of the Effectors

Receive signals from the control centre and execute the necessary corrective changes to return the variable to balance

Feedback loops

Regulate and maintain different functions in the body to keep the systems in physiological balance.

Negative feedback loop

Once a variable is detected as higher/lower than required, negative feedback ensures that this variable is decreased or increased to return to the set point. Once homeostasis has been achieved, this is fed back by the effector system and the stimulus ceases to exist.

Positive feedback loop

Describes a chain of positive events in which the output of the process increases the input that started it until completion. It amplifies the initial change until an ultimate endpoint or biological goal is achieved.

How does negative feedback link to midwifery practice?

Neonatal thermoregulation. Newborn’s skin detects heat loss to the cooler external environment and alert the hypothalamus. The body activates corrective effectors- inducing peripheral vasoconstriction and non-shivering thermogenesis via brown adipose tissue- to restore core temperature back to its set point, at which point the heat-generating response scales down.

How does positive feedback link to midwifery practice?

The Ferguson reflex during labour. As the fetal presenting part descends and presses against the cervix, stretch receptors trigger afferent signals to the hypothalamus, prompting the posterior pituitary to release oxytocin. Oxytocin stimulates stronger myometrial contractions, pushing the fetus further into the lower uterine segment, creating even greater cervical stretch and releasing further oxytocin in an escalating cycle that concludes only with the birth of the baby and placenta.